Added handling for creating broken symlinks with trailing separator

- fixes pytest-dev#371

pyfakefs/fake_filesystem.py

@@ -2459,8 +2459,20 @@ def create_symlink(self, file_path, link_target, create_missing_dirs=True):
         if self.ends_with_path_separator(file_path):
             if self.exists(file_path):
                 self.raise_os_error(errno.EEXIST, file_path)
-            if not self.is_windows_fs:
-                self.raise_os_error(errno.ENOENT, file_path)
+            if self.exists(link_target):
+                if not self.is_windows_fs:
+                    self.raise_os_error(errno.ENOENT, file_path)
+            else:
+                if self.is_windows_fs:
+                    self.raise_os_error(errno.EINVAL, link_target)
+                elif self.is_macos:
+                    # to avoid EEXIST exception, remove the link
+                    # if it already exists
+                    if self.exists(file_path, check_link=True):
+                        self.remove_object(file_path)
+                else:
+                    self.raise_os_error(errno.EEXIST, link_target)
+
 
         # resolve the link path only if it is not a link itself
         if not self.islink(file_path):

pyfakefs/tests/fake_os_test.py

@@ -612,6 +612,31 @@ def test_readlink_raises_if_path_is_none(self):
         self.skip_if_symlink_not_supported()
         self.assertRaises(TypeError, self.os.readlink, None)
 
+    def test_broken_symlink_with_trailing_separator_linux(self):
+        self.check_linux_only()
+        file_path = self.make_path('foo')
+        link_path = self.make_path('link')
+        self.os.symlink(file_path, link_path)
+        self.assert_raises_os_error(errno.EEXIST, self.os.symlink,
+            link_path + self.os.sep, link_path + self.os.sep)
+
+    def test_broken_symlink_with_trailing_separator_macos(self):
+        # regression test for #371
+        self.check_macos_only()
+        file_path = self.make_path('foo')
+        link_path = self.make_path('link')
+        self.os.symlink(file_path, link_path)
+        self.os.symlink(link_path + self.os.sep, link_path + self.os.sep)
+
+    def test_broken_symlink_with_trailing_separator_windows(self):
+        self.check_windows_only()
+        self.skip_if_symlink_not_supported()
+        file_path = self.make_path('foo')
+        link_path = self.make_path('link')
+        self.os.symlink(file_path, link_path)
+        self.assert_raises_os_error(errno.EINVAL, self.os.symlink,
+            link_path + self.os.sep, link_path + self.os.sep)
+
     def test_readlink_with_links_in_path(self):
         self.skip_if_symlink_not_supported()
         self.create_symlink(self.make_path('meyer', 'lemon', 'pie'),