diff --git a/.isort.cfg b/.isort.cfg
index b90ca30c..7734b47c 100644
--- a/.isort.cfg
+++ b/.isort.cfg
@@ -1,2 +1,2 @@
 [settings]
-known_third_party = cf_units,cftime,httpretty,isodate,lxml,netCDF4,numpy,owslib,pendulum,pkg_resources,pygeoif,pyproj,pytest,regex,requests,setuptools,validators
+known_third_party = cf_units,cftime,distutils,httpretty,isodate,lxml,netCDF4,numpy,owslib,pendulum,pkg_resources,pygeoif,pyproj,pytest,regex,requests,requests_mock,setuptools,shapely,validators
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index d60f6b78..0b2bd1f4 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -11,27 +11,20 @@ repos:
     - id: check-docstring-first
     - id: check-added-large-files
     - id: requirements-txt-fixer
-    - id: file-contents-sorter
-      files: test_requirements.txt
 
-- repo: https://gitlab.com/pycqa/flake8
-  rev: 3.9.2
+- repo: https://github.com/PyCQA/flake8
+  rev: 4.0.1
   hooks:
     - id: flake8
       exclude: docs/source/conf.py
       args: [--max-line-length=200, "--ignore=E203,E501,W503", "--select=select=C,E,F,W,B,B950"]
 
-- repo: https://github.com/pre-commit/mirrors-isort
-  rev: v5.10.1
+- repo: https://github.com/pycqa/isort
+  rev: 5.10.1
   hooks:
   - id: isort
     additional_dependencies: [toml]
-    args: [--project=compliance_checker, --multi-line=3, --lines-after-imports=2, --lines-between-types=1, --trailing-comma, --force-grid-wrap=0, --use-parentheses, --line-width=88]
-
-- repo: https://github.com/asottile/seed-isort-config
-  rev: v2.2.0
-  hooks:
-    - id: seed-isort-config
+    args: ["--profile", "black", "--filter-files"]
 
 - repo: https://github.com/psf/black
   rev: 22.3.0
diff --git a/cchecker.py b/cchecker.py
index 243fc737..4155f057 100755
--- a/cchecker.py
+++ b/cchecker.py
@@ -3,7 +3,6 @@
 import argparse
 import sys
 import warnings
-
 from collections import defaultdict
 from textwrap import dedent
 
diff --git a/compliance_checker/__init__.py b/compliance_checker/__init__.py
index a51d505e..1a25bdef 100644
--- a/compliance_checker/__init__.py
+++ b/compliance_checker/__init__.py
@@ -5,7 +5,6 @@
 
 from netCDF4 import Dataset
 
-
 try:
     from ._version import __version__
 except ImportError:
diff --git a/compliance_checker/acdd.py b/compliance_checker/acdd.py
index 7f490df5..40bcfbd1 100644
--- a/compliance_checker/acdd.py
+++ b/compliance_checker/acdd.py
@@ -10,7 +10,6 @@
 
 import numpy as np
 import pendulum
-
 from cftime import num2pydate
 from pygeoif import from_wkt
 
@@ -582,7 +581,7 @@ def check_time_extents(self, ds):
         try:
             t_min = dateparse(ds.time_coverage_start)
             t_max = dateparse(ds.time_coverage_end)
-        except:
+        except (TypeError, pendulum.parsing.exceptions.ParserError):
             return Result(
                 BaseCheck.MEDIUM,
                 False,
@@ -618,7 +617,7 @@ def check_time_extents(self, ds):
                 num2pydate(ds.variables[timevar][-1], ds.variables[timevar].units),
                 "UTC",
             )
-        except:
+        except ValueError:
             return Result(
                 BaseCheck.MEDIUM,
                 False,
@@ -829,7 +828,8 @@ def check_var_coverage_content_type(self, ds):
             }
             if ctype not in valid_ctypes:
                 msgs.append(
-                    'coverage_content_type "%s" not in %s' % (variable, sorted(valid_ctypes))
+                    'coverage_content_type "%s" not in %s'
+                    % (variable, sorted(valid_ctypes))
                 )
                 results.append(
                     Result(
diff --git a/compliance_checker/base.py b/compliance_checker/base.py
index 6bebcd8a..acd080bd 100644
--- a/compliance_checker/base.py
+++ b/compliance_checker/base.py
@@ -8,13 +8,11 @@
 import pprint
 import re
 import warnings
-
 from collections import defaultdict
 from functools import wraps
 from io import StringIO
 
 import validators
-
 from lxml import etree
 from netCDF4 import Dataset
 from owslib.namespaces import Namespaces
@@ -22,11 +20,9 @@
 from owslib.swe.sensor.sml import SensorML
 
 import compliance_checker.cfutil as cfutil
-
 from compliance_checker import MemoizedDataset, __version__
 from compliance_checker.util import kvp_convert
 
-
 # Python 3.5+ should work, also have a fallback
 try:
     from typing import Pattern
diff --git a/compliance_checker/cf/__init__.py b/compliance_checker/cf/__init__.py
index 573f9508..1baa8d5d 100644
--- a/compliance_checker/cf/__init__.py
+++ b/compliance_checker/cf/__init__.py
@@ -1,10 +1,9 @@
+from compliance_checker.cf import util
 from compliance_checker.cf.appendix_d import (
     dimless_vertical_coordinates_1_6,
     dimless_vertical_coordinates_1_7,
 )
 from compliance_checker.cf.cf import CF1_6Check, CF1_7Check
-from compliance_checker.cf import util
-
 
 __all__ = [
     "CF1_6Check",
diff --git a/compliance_checker/cf/cf.py b/compliance_checker/cf/cf.py
index 747e3b23..41b8d8ab 100644
--- a/compliance_checker/cf/cf.py
+++ b/compliance_checker/cf/cf.py
@@ -2,17 +2,22 @@
 # -*- coding: utf-8 -*-
 
 from compliance_checker import cfutil  # noqa: F401
-from compliance_checker.base import BaseCheck, BaseNCCheck, Result, TestCtx  # noqa: F401
+from compliance_checker.base import (  # noqa: F401
+    BaseCheck,
+    BaseNCCheck,
+    Result,
+    TestCtx,
+)
 from compliance_checker.cf import util  # noqa: F401
 from compliance_checker.cf.appendix_d import (  # noqa: F401
     dimless_vertical_coordinates_1_6,
     dimless_vertical_coordinates_1_7,
     no_missing_terms,
 )
-
-from compliance_checker.cf.appendix_e import cell_methods16, cell_methods17  # noqa: F401
+from compliance_checker.cf.appendix_e import cell_methods16  # noqa: F401
+from compliance_checker.cf.appendix_e import cell_methods17  # noqa: F401
+from compliance_checker.cf.appendix_f import ellipsoid_names17  # noqa: F401
 from compliance_checker.cf.appendix_f import (  # noqa: F401
-    ellipsoid_names17,
     grid_mapping_attr_types16,
     grid_mapping_attr_types17,
     grid_mapping_dict16,
diff --git a/compliance_checker/cf/cf_1_6.py b/compliance_checker/cf/cf_1_6.py
index fb87b1d6..a4006b09 100644
--- a/compliance_checker/cf/cf_1_6.py
+++ b/compliance_checker/cf/cf_1_6.py
@@ -1,27 +1,22 @@
+import difflib
 import logging
-
 from collections import defaultdict
 
 import numpy as np
 import regex
-
 from cf_units import Unit
 
 from compliance_checker import cfutil
 from compliance_checker.base import BaseCheck, Result, TestCtx
 from compliance_checker.cf import util
 from compliance_checker.cf.appendix_c import valid_modifiers
-from compliance_checker.cf.appendix_d import (
-    dimless_vertical_coordinates_1_6,
-)
+from compliance_checker.cf.appendix_d import dimless_vertical_coordinates_1_6
 from compliance_checker.cf.appendix_e import cell_methods16
 from compliance_checker.cf.appendix_f import (
     grid_mapping_attr_types16,
     grid_mapping_dict16,
 )
-
 from compliance_checker.cf.cf_base import CFNCCheck, appendix_a_base
-import difflib
 
 logger = logging.getLogger(__name__)
 
diff --git a/compliance_checker/cf/cf_1_7.py b/compliance_checker/cf/cf_1_7.py
index c4728189..0729dacb 100644
--- a/compliance_checker/cf/cf_1_7.py
+++ b/compliance_checker/cf/cf_1_7.py
@@ -1,19 +1,15 @@
 import logging
 import os
 import sqlite3
-
 from warnings import warn
 
 import numpy as np
 import pyproj
 import regex
 
-
 from compliance_checker import cfutil
 from compliance_checker.base import BaseCheck, Result, TestCtx
-from compliance_checker.cf.appendix_d import (
-    dimless_vertical_coordinates_1_7,
-)
+from compliance_checker.cf.appendix_d import dimless_vertical_coordinates_1_7
 from compliance_checker.cf.appendix_e import cell_methods17
 from compliance_checker.cf.appendix_f import (
     ellipsoid_names17,
@@ -22,8 +18,8 @@
     horizontal_datum_names17,
     prime_meridian_names17,
 )
-from compliance_checker.cf.cf_base import appendix_a_base
 from compliance_checker.cf.cf_1_6 import CF1_6Check
+from compliance_checker.cf.cf_base import appendix_a_base
 
 logger = logging.getLogger(__name__)
 
diff --git a/compliance_checker/cf/cf_1_8.py b/compliance_checker/cf/cf_1_8.py
index f2a15548..fc666cc1 100644
--- a/compliance_checker/cf/cf_1_8.py
+++ b/compliance_checker/cf/cf_1_8.py
@@ -1,16 +1,3 @@
-from compliance_checker.base import BaseCheck, TestCtx
-from compliance_checker import MemoizedDataset
-from compliance_checker.cf.cf_1_7 import CF1_7Check
-from netCDF4 import Dataset
-import requests
-from lxml import etree
-from shapely.geometry import Polygon
-import numpy as np
-import re
-from compliance_checker.cf.util import reference_attr_variables, string_from_var_type
-import itertools
-import warnings
-
 """
 What's new in CF-1.8
 --------------------
@@ -23,6 +10,21 @@
 7.5. Geometries
 """
 
+import itertools
+import re
+import warnings
+
+import numpy as np
+import requests
+from lxml import etree
+from netCDF4 import Dataset
+from shapely.geometry import Polygon
+
+from compliance_checker import MemoizedDataset
+from compliance_checker.base import BaseCheck, TestCtx
+from compliance_checker.cf.cf_1_7 import CF1_7Check
+from compliance_checker.cf.util import reference_attr_variables, string_from_var_type
+
 
 class CF1_8Check(CF1_7Check):
     """Implementation for CF v1.8. Inherits from CF1_7Check."""
@@ -249,9 +251,7 @@ def match_taxa_standard_names(standard_name_string):
             return (
                 standard_name_string is not None
                 and "taxon" in standard_name_string
-                and
-                # exclude the identifiers we just looked at
-                standard_name_string
+                and standard_name_string  # exclude the identifiers we just looked at
                 not in {"biological_taxon_lsid", "biological_taxon_name"}
                 and standard_name_string in self._std_names
             )
@@ -400,7 +400,7 @@ def handle_lsid(self, taxon_lsid_variable, taxon_name_variable):
                         timeout=15,
                     )
                     response.raise_for_status()
-                except requests.exceptions.RequestException as e:
+                except requests.exceptions.RequestException as e:  # noqa: F841
                     messages.append(
                         "Aphia ID {taxon_match['object_id'] returned "
                         "other error: {str(e)}"
@@ -471,267 +471,6 @@ def handle_lsid(self, taxon_lsid_variable, taxon_name_variable):
         return messages
 
 
-class GeometryStorage(object):
-    """Abstract base class for geometries"""
-
-    def __init__(self, coord_vars, node_count):
-        self.coord_vars = coord_vars
-        self.node_count = node_count
-        self.errors = []
-        # geometry is later parsed after sanity checks are run
-        self.geometry = None
-
-    def _split_mulitpart_geometry(self):
-        arr_extents_filt = self.part_node_count[self.part_node_count > 0]
-        splits = np.split(np.vstack(self.coord_vars).T, arr_extents_filt.cumsum()[:-1])
-        return splits
-
-
-class PointGeometry(GeometryStorage):
-    """Class for validating Point/MultiPoint geometries"""
-
-    def check_geometry(self):
-        super().check_geometry()
-        # non-multipoint should have exactly one feature
-        if self.node_count is None:
-            pass
-        else:
-            self.node_count
-
-        if all(len(cv.dimensions) != 0 for cv in self.coord_vars):
-            same_dim_group = itertools.groupby(self.coord_vars, lambda x: x.dimensions)
-            same_dim = next(same_dim_group, True) and not next(same_dim_group, False)
-            if not same_dim:
-                self.errors.append(
-                    "For a point geometry, coordinate "
-                    "variables must be the same length as "
-                    "node_count defined, or must be "
-                    "length 1 if node_count is not set"
-                )
-        return self.errors
-
-
-class LineGeometry(GeometryStorage):
-    """Class for validating Line/MultiLine geometries"""
-
-    def __init__(self, coord_vars, node_count, part_node_count):
-        super().__init__(coord_vars, node_count)
-        self.part_node_count = part_node_count
-        if not np.issubdtype(self.node_count.dtype, np.integer):
-            raise TypeError("For line geometries, node_count must be an integer")
-
-    def check_geometry(self):
-        geom_errors = []
-        same_dim_group = itertools.groupby(self.coord_vars, lambda x: x.dimensions)
-        same_dim = next(same_dim_group, True) and not next(same_dim_group, False)
-        if not same_dim:
-            raise IndexError(
-                "Coordinate variables must be the same length. "
-                "If node_count is specified, this value must "
-                "also sum to the length of the coordinate "
-                "variables."
-            )
-        # if a multipart
-        if self.node_count is not None:
-            same_length = len(self.coord_vars[0]) == self.node_count[:].sum()
-            if not same_length:
-                geom_errors.append(
-                    "Coordinate variables must be the same "
-                    "length. If node_count is specified, this "
-                    "value must also sum to the length of the "
-                    "coordinate variables."
-                )
-        if self.part_node_count is not None:
-            if not np.issubdtype(self.part_node_count.dtype, np.integer):
-                geom_errors.append(
-                    "when part_node_count is specified, it must "
-                    "be an array of integers"
-                )
-            same_node_count = len(self.coord_vars[0]) == self.node_count[:].sum()
-            if not same_node_count:
-                geom_errors.append(
-                    "The sum of part_node_count must be equal "
-                    "to the value of node_count"
-                )
-        return geom_errors
-
-
-class PolygonGeometry(LineGeometry):
-    """Class for validating Line/MultiLine geometries"""
-
-    # TODO/clarify: Should polygons be simple, i.e. non-self intersecting?
-    # Presumably
-    def __init__(self, coord_vars, node_count, part_node_count, interior_ring):
-        super().__init__(coord_vars, node_count, part_node_count)
-        self.part_node_count = part_node_count
-        self.interior_ring = interior_ring
-
-    def check_polygon_orientation(self, transposed_coords, interior=False):
-        """
-        Checks that the polygon orientation is counter-clockwise if an
-        exterior ring, otherwise clockwise if an interior ring.  Orientation
-        is indicated by the `interior` boolean variable with False for an
-        exterior ring and True for an interior ring (hole), defaulting to False.
-        This function operates piecewise on individual interior/exterior
-        polygons as well as multipart polygons
-        :param np.array transposed_coords: A 2-by-n array of x and y coordinates
-        :param bool interior: A boolean defaulting to False which has False
-        indicating a counter-clockwise or exterior polygon, and True
-        indicating a clockwise or interior polygon.
-        :rtype bool:
-        :returns: True if the polygon follows the proper orientation,
-                  False if it fails the orientation test.
-        """
-
-        try:
-            polygon = Polygon(transposed_coords.tolist())
-        except ValueError:
-            raise ValueError(
-                "Polygon contains too few points to perform orientation test"
-            )
-
-        ccw = polygon.exterior.is_ccw
-        return not ccw if interior else ccw
-
-    def check_geometry(self):
-        messages = super().check_geometry()
-        # If any errors occurred within the preliminary checks, they preclude
-        # running checks against the geometry here.
-        if messages:
-            return messages
-        if self.part_node_count is not None:
-            extents = np.concatenate([np.array([0]), self.part_node_count[:].cumsum()])
-            if self.interior_ring is not None:
-                ring_orientation = self.interior_ring[:].astype(bool)
-            else:
-                ring_orientation = np.zeros(len(self.part_count), dtype=bool)
-            node_indexer_len = len(self.part_node_count)
-        else:
-            extents = np.concatenate([np.array([0]), self.node_count[:].cumsum()])
-            node_indexer_len = len(self.node_count)
-            ring_orientation = np.zeros(node_indexer_len, dtype=bool)
-        # TODO: is it necessary to check whether part_node_count "consumes"
-        #       node_count in the polygon, i.e. first (3, 3, 3) will consume
-        #       a node part of 9, follow by next 3 will consume a node part of
-        #       3 after consuming
-        for i in range(node_indexer_len):
-            extent_slice = slice(extents[i], extents[i + 1])
-            poly_sliced = np.vstack([cv[extent_slice] for cv in self.coord_vars]).T
-            pass_orientation = self.check_polygon_orientation(
-                poly_sliced, ring_orientation[i]
-            )
-            if not pass_orientation:
-                orient_fix = (
-                    ("exterior", "counterclockwise")
-                    if not ring_orientation[i]
-                    else ("interior", "clockwise")
-                )
-                message = (
-                    f"An {orient_fix[0]} polygon referred to by "
-                    f"coordinates ({poly_sliced}) must have coordinates "
-                    f"in {orient_fix[1]} order"
-                )
-                messages.append(message)
-        return messages
-
-    def check_geometry(self, ds: Dataset):
-        """Runs any necessary checks for geometry well-formedness
-        :param netCDF4.Dataset ds: An open netCDF dataset
-        :returns list: List of error messages
-
-        """
-        vars_with_geometry = ds.get_variables_by_attributes(
-            geometry=lambda g: g is not None
-        )
-        results = []
-        unique_geometry_var_names = {var.geometry for var in vars_with_geometry}
-        if unique_geometry_var_names:
-            geom_valid = TestCtx(BaseCheck.MEDIUM, self.section_titles["7.5"])
-            geom_valid.out_of += 1
-        for geometry_var_name in unique_geometry_var_names:
-            if geometry_var_name not in ds.variables:
-                geom_valid.messages.append(
-                    "Cannot find geometry variable " f"named {geometry_var_name}"
-                )
-                results.append(geom_valid.to_result())
-                continue
-            else:
-                geometry_var = ds.variables[geometry_var_name]
-
-            geometry_type = getattr(geometry_var, "geometry_type")
-            try:
-                node_coord_var_names = geometry_var.node_coordinates
-            except AttributeError:
-                geom_valid.messages.append(
-                    "Could not find required attribute "
-                    '"node_coordinates" in geometry '
-                    f'variable "{geometry_var_name}"'
-                )
-                results.append(geom_valid.to_result())
-                continue
-            if not isinstance(node_coord_var_names, str):
-                geom_valid.messages.append(
-                    'Attribute "node_coordinates" in geometry '
-                    f'variable "{geometry_var_name}" must be '
-                    "a string"
-                )
-                results.append(geom_valid.to_result())
-                continue
-            split_coord_names = node_coord_var_names.strip().split(" ")
-            node_coord_vars, not_found_node_vars = [], []
-            for coord_var_name in split_coord_names:
-                try:
-                    node_coord_vars.append(ds.variables[coord_var_name])
-                except KeyError:
-                    not_found_node_vars.append(coord_var_name)
-            # If any variables weren't found, we can't continue
-            if not_found_node_vars:
-                geom_valid.messages.append(
-                    "The following referenced node coordinate"
-                    "variables for geometry variable"
-                    f'"{geometry_var_name}" were not found: '
-                    f"{not_found_node_vars}"
-                )
-                results.append(geom_valid.to_result())
-                continue
-
-            node_count = reference_attr_variables(
-                ds, getattr(geometry_var, "node_count", None)
-            )
-            # multipart lines and polygons only
-            part_node_count = reference_attr_variables(
-                ds, getattr(geometry_var, "part_node_count", None)
-            )
-            # polygons with interior geometry only
-            interior_ring = reference_attr_variables(
-                ds, getattr(geometry_var, "interior_ring", None)
-            )
-
-            if geometry_type == "point":
-                geometry = PointGeometry(node_coord_vars, node_count)
-            elif geometry_type == "line":
-                geometry = LineGeometry(node_coord_vars, node_count, part_node_count)
-            elif geometry_type == "polygon":
-                geometry = PolygonGeometry(
-                    node_coord_vars, node_count, part_node_count, interior_ring
-                )
-            else:
-                geom_valid.messages.append(
-                    f'For geometry variable "{geometry_var_name}'
-                    'the attribute "geometry_type" must exist'
-                    "and have one of the following values:"
-                    '"point", "line", "polygon"'
-                )
-                results.append(geom_valid.to_result())
-                continue
-            # check geometry
-            geometry.check_geometry()
-            if not geometry.errors:  # geom_valid.messages:
-                geom_valid.score += 1
-            results.append(geom_valid.to_result())
-        return results
-
-
 class GeometryStorage(object):
     """Abstract base class for geometries"""
 
diff --git a/compliance_checker/cf/cf_base.py b/compliance_checker/cf/cf_base.py
index 895d2089..07f0ca70 100644
--- a/compliance_checker/cf/cf_base.py
+++ b/compliance_checker/cf/cf_base.py
@@ -3,20 +3,16 @@
 import logging
 import os
 import sys
-
 from collections import OrderedDict, defaultdict
 from warnings import warn
 
 import numpy as np
 import regex
 
-
 from compliance_checker import cfutil
 from compliance_checker.base import BaseCheck, BaseNCCheck, Result, TestCtx
 from compliance_checker.cf import util
-from compliance_checker.cf.appendix_d import (
-    no_missing_terms,
-)
+from compliance_checker.cf.appendix_d import no_missing_terms
 
 logger = logging.getLogger(__name__)
 
diff --git a/compliance_checker/cf/util.py b/compliance_checker/cf/util.py
index e36966fe..e600fa99 100644
--- a/compliance_checker/cf/util.py
+++ b/compliance_checker/cf/util.py
@@ -2,7 +2,6 @@
 import itertools
 import os
 import sys
-
 from collections import defaultdict
 from copy import deepcopy
 from pkgutil import get_data
@@ -10,13 +9,11 @@
 
 import lxml.html
 import requests
-
 from cf_units import Unit
 from lxml import etree
 from netCDF4 import Dataset, Dimension, Variable
 from pkg_resources import resource_filename
 
-
 # copied from paegan
 # paegan may depend on these later
 _possiblet = {
diff --git a/compliance_checker/cfutil.py b/compliance_checker/cfutil.py
index da5f8390..a5c322bb 100644
--- a/compliance_checker/cfutil.py
+++ b/compliance_checker/cfutil.py
@@ -6,14 +6,12 @@
 import csv
 import re
 import warnings
-
 from collections import defaultdict
 from functools import lru_cache, partial
 
 from cf_units import Unit
 from pkg_resources import resource_filename
 
-
 _UNITLESS_DB = None
 _SEA_NAMES = None
 
diff --git a/compliance_checker/ioos.py b/compliance_checker/ioos.py
index 6c9a1654..73c2fbee 100644
--- a/compliance_checker/ioos.py
+++ b/compliance_checker/ioos.py
@@ -2,11 +2,9 @@
 Check for IOOS-approved attributes
 """
 import re
-
 from numbers import Number
 
 import validators
-
 from cf_units import Unit
 from lxml.etree import XPath
 from owslib.namespaces import Namespaces
@@ -426,10 +424,9 @@ class NamingAuthorityValidator(base.UrlValidator):
 
     def validator_func(self, input_value):
         return (
+            # also check for reverse DNS strings
             super().validator_func(input_value)
-            or
-            # check for reverse DNS strings
-            validators.domain(".".join(input_value.split(".")[::-1]))
+            or validators.domain(".".join(input_value.split(".")[::-1]))
         )
 
 
diff --git a/compliance_checker/protocols/netcdf.py b/compliance_checker/protocols/netcdf.py
index 65c58748..519f132d 100644
--- a/compliance_checker/protocols/netcdf.py
+++ b/compliance_checker/protocols/netcdf.py
@@ -5,6 +5,8 @@
 Functions to assist in determining if the URL points to a netCDF file
 """
 
+import warnings
+
 import requests
 
 
@@ -79,7 +81,10 @@ def is_remote_netcdf(ds_str):
     try:
         head_req = requests.head(ds_str, allow_redirects=True, timeout=10)
         head_req.raise_for_status()
-    except:
+    except requests.exceptions.RequestException as e:
+        warnings.warn(
+            "Received exception when making HEAD request to {}: {}".format(ds_str, e)
+        )
         content_type = None
     else:
         content_type = head_req.headers.get("content-type")
diff --git a/compliance_checker/runner.py b/compliance_checker/runner.py
index 9755318d..928aee3a 100644
--- a/compliance_checker/runner.py
+++ b/compliance_checker/runner.py
@@ -3,7 +3,6 @@
 import os
 import sys
 import traceback
-
 from collections import OrderedDict
 from contextlib import contextmanager
 
diff --git a/compliance_checker/suite.py b/compliance_checker/suite.py
index 35cf82b2..ca3d0782 100644
--- a/compliance_checker/suite.py
+++ b/compliance_checker/suite.py
@@ -11,16 +11,14 @@
 import sys
 import textwrap
 import warnings
-
 from collections import defaultdict
 from datetime import datetime, timezone
-from distutils.version import StrictVersion
 from operator import itemgetter
 from pathlib import Path
 from urllib.parse import urlparse
 
 import requests
-
+from distutils.version import StrictVersion
 from lxml import etree as ET
 from netCDF4 import Dataset
 from owslib.sos import SensorObservationService
@@ -31,7 +29,6 @@
 from compliance_checker.base import BaseCheck, GenericFile, Result, fix_return_value
 from compliance_checker.protocols import cdl, netcdf, opendap
 
-
 # Ensure output is encoded as Unicode when checker output is redirected or piped
 if sys.stdout.encoding is None:
     sys.stdout = codecs.getwriter("utf8")(sys.stdout)
diff --git a/compliance_checker/tests/conftest.py b/compliance_checker/tests/conftest.py
index 94e8e5c0..c83e5f44 100644
--- a/compliance_checker/tests/conftest.py
+++ b/compliance_checker/tests/conftest.py
@@ -1,11 +1,9 @@
 import os
 import subprocess
-
 from itertools import chain
 from pathlib import Path
 
 import pytest
-
 from netCDF4 import Dataset
 from pkg_resources import resource_filename
 
diff --git a/compliance_checker/tests/test_acdd.py b/compliance_checker/tests/test_acdd.py
index 4e9ea6e8..453ce58c 100644
--- a/compliance_checker/tests/test_acdd.py
+++ b/compliance_checker/tests/test_acdd.py
@@ -1,7 +1,6 @@
 import os
 
 import numpy as np
-
 from netCDF4 import Dataset
 
 from compliance_checker.acdd import ACDD1_1Check, ACDD1_3Check
@@ -15,7 +14,9 @@ def to_singleton_var(item):
     Get the first value of a list if this implements iterator protocol and is
     not a string
     """
-    return [x[0] if hasattr(x, "__iter__") and not isinstance(x, str) else x for x in item]
+    return [
+        x[0] if hasattr(x, "__iter__") and not isinstance(x, str) else x for x in item
+    ]
 
 
 def check_varset_nonintersect(group0, group1):
diff --git a/compliance_checker/tests/test_base.py b/compliance_checker/tests/test_base.py
index e0faf557..87b30735 100644
--- a/compliance_checker/tests/test_base.py
+++ b/compliance_checker/tests/test_base.py
@@ -3,7 +3,6 @@
 """Tests for base compliance checker class"""
 
 import os
-
 from unittest import TestCase
 
 from netCDF4 import Dataset
diff --git a/compliance_checker/tests/test_cf.py b/compliance_checker/tests/test_cf.py
index 9fd18185..d4563794 100644
--- a/compliance_checker/tests/test_cf.py
+++ b/compliance_checker/tests/test_cf.py
@@ -2,18 +2,20 @@
 # -*- coding: utf-8 -*-
 
 import copy
+import json
 import os
+import re
 import sqlite3
-
 from itertools import chain
 from tempfile import gettempdir
 
 import numpy as np
 import pytest
-
+import requests_mock
 from netCDF4 import Dataset, stringtoarr
 
 from compliance_checker import cfutil
+from compliance_checker.cf.appendix_d import no_missing_terms
 from compliance_checker.cf.cf import (
     CF1_6Check,
     CF1_7Check,
@@ -21,7 +23,6 @@
     dimless_vertical_coordinates_1_6,
     dimless_vertical_coordinates_1_7,
 )
-from compliance_checker.cf.appendix_d import no_missing_terms
 from compliance_checker.cf.util import (
     StandardNameTable,
     create_cached_data_dir,
@@ -38,9 +39,6 @@
     MockTimeSeries,
     MockVariable,
 )
-import requests_mock
-import json
-import re
 from compliance_checker.tests.resources import STATIC_FILES
 
 
diff --git a/compliance_checker/tests/test_cf_integration.py b/compliance_checker/tests/test_cf_integration.py
index b6a01b9c..ab1e849d 100644
--- a/compliance_checker/tests/test_cf_integration.py
+++ b/compliance_checker/tests/test_cf_integration.py
@@ -3,10 +3,8 @@
 
 import pytest
 
-
 from compliance_checker.cf import util
 
-
 # get current std names table version (it changes)
 std_names = util.StandardNameTable()
 
diff --git a/compliance_checker/tests/test_cli.py b/compliance_checker/tests/test_cli.py
index c12c3c1c..42682d9b 100644
--- a/compliance_checker/tests/test_cli.py
+++ b/compliance_checker/tests/test_cli.py
@@ -8,7 +8,6 @@
 import json
 import os
 import sys
-
 from argparse import Namespace
 
 import pytest
diff --git a/compliance_checker/tests/test_ioos_profile.py b/compliance_checker/tests/test_ioos_profile.py
index 2ecad34e..9f8d2db9 100644
--- a/compliance_checker/tests/test_ioos_profile.py
+++ b/compliance_checker/tests/test_ioos_profile.py
@@ -1,7 +1,6 @@
 import os
 
 import numpy as np
-
 from netCDF4 import Dataset
 
 from compliance_checker.ioos import (
diff --git a/compliance_checker/tests/test_ioos_sos.py b/compliance_checker/tests/test_ioos_sos.py
index 9f360f36..8b82f1f5 100644
--- a/compliance_checker/tests/test_ioos_sos.py
+++ b/compliance_checker/tests/test_ioos_sos.py
@@ -27,9 +27,9 @@ def test_retrieve_getcaps(self):
         httpretty.register_uri(
             httpretty.GET, url, content_type="text/xml", body=self.resp
         )
-        # need to mock out the HEAD response so that compliance checker
-        # recognizes this as some sort of XML doc instead of an OPeNDAP
-        # source
+        httpretty.register_uri(
+            httpretty.HEAD, url, content_type="text/xml", body="HTTP/1.1 200"
+        )
         ComplianceChecker.run_checker(url, ["ioos_sos"], 1, "normal")
 
 
@@ -59,6 +59,9 @@ def test_retrieve_describesensor(self):
         httpretty.register_uri(
             httpretty.GET, url, content_type="text/xml", body=self.resp
         )
+        httpretty.register_uri(
+            httpretty.HEAD, url, content_type="text/xml", body="HTTP/1.1 200"
+        )
         # need to mock out the HEAD response so that compliance checker
         # recognizes this as some sort of XML doc instead of an OPeNDAP
         # source
diff --git a/compliance_checker/tests/test_suite.py b/compliance_checker/tests/test_suite.py
index 325c1f86..bc79b0a9 100644
--- a/compliance_checker/tests/test_suite.py
+++ b/compliance_checker/tests/test_suite.py
@@ -1,17 +1,14 @@
 # coding=utf-8
 import os
 import unittest
-
 from pathlib import Path
 
 import numpy as np
-
 from pkg_resources import resource_filename
 
 from compliance_checker.base import BaseCheck, GenericFile, Result
 from compliance_checker.suite import CheckSuite
 
-
 static_files = {
     "2dim": resource_filename("compliance_checker", "tests/data/2dim-grid.nc"),
     "bad_region": resource_filename("compliance_checker", "tests/data/bad_region.nc"),
@@ -224,7 +221,7 @@ def test_cdl_file(self):
 
     def test_load_local_dataset_GenericFile(self):
         resp = self.cs.load_local_dataset(static_files["empty"])
-        assert isinstance(resp, GenericFile) == True
+        assert isinstance(resp, GenericFile)
 
     def test_standard_output_score_header(self):
         """
diff --git a/compliance_checker/util.py b/compliance_checker/util.py
index a9bb16ee..8117ad3e 100644
--- a/compliance_checker/util.py
+++ b/compliance_checker/util.py
@@ -15,7 +15,8 @@ def datetime_is_iso(date_str):
         else:
             isodate.parse_date(date_str)
         return True, []
-    except:  # Any error qualifies as not ISO format
+    # The following errors qualify as non ISO8601 format
+    except (TypeError, AttributeError, ValueError, isodate.ISO8601Error):
         return False, ["Datetime provided is not in a valid ISO 8601 format"]
 
 
@@ -43,6 +44,6 @@ def kvp_convert(input_coll):
         return input_coll
     else:
         return OrderedDict(
-            (thing, None) if not isinstance(thing, tuple) else
-            (thing[0], thing[1]) for thing in input_coll
+            (thing, None) if not isinstance(thing, tuple) else (thing[0], thing[1])
+            for thing in input_coll
         )
diff --git a/pyproject.toml b/pyproject.toml
index 7825e3d5..3856b400 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -7,3 +7,6 @@ markers = [
     "integration: marks integration tests (deselect with '-m \"not integration\"')",
     "slowtest: marks slow tests (deselect with '-m \"not slowtest\"')"
 ]
+
+[tool.isort]
+profile = "black"
diff --git a/requirements.txt b/requirements.txt
index 5a591098..144e32d6 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -11,5 +11,5 @@ pyproj>=2.2.1
 regex>=2017.07.28
 requests>=2.2.1
 setuptools>=15.0
-validators>=0.14.2
 shapely>=1.7.1
+validators>=0.14.2
diff --git a/test_requirements.txt b/test_requirements.txt
index 656a55f1..4875429d 100644
--- a/test_requirements.txt
+++ b/test_requirements.txt
@@ -1,9 +1,9 @@
+codecov
 codespell
 flake8
 httpretty
 mypy
 pre-commit
 pytest>=2.9.0
+pytest-cov>=3.0.0
 requests-mock>=1.7.0
-codecov
-pytest-cov