Overridden method called instead of base class method

[slozier]

The following throws an exception instead of succeeding:

from io import BytesIO
f = BytesIO()
f.read()

class MyBytesIO(BytesIO):
    def read(self, n=None):
        raise Exception

f = MyBytesIO()
BytesIO.read(f)

See also #1129 and #1070.

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Ran into this issue when trying to run:

make.ps1 test-"CPython.test_iter|IronPython.test_io_stdlib"

In this case it was causing a StackOverflowException:

from io import BytesIO
f = BytesIO()
f.read()

class MyBytesIO(BytesIO):
    def read(self, n=None):
        return super().read(n)

f = MyBytesIO()
f.read()