Patch by Sébastien Sablé.

an ImportError. Rearranged the import, faked out the implementation when
the import fails, and reorganized a test that depends on Win32 behavior.

test cases now also have assertWarns and assertWarnsRegexp methods to
check that a given warning type was triggered by the code under test.

view of their contents without duplicating them.  The view is both readable
and writable.

This uses the GetFileInformationByHandle function to return a tuple of values
to identify a file, then ntpath.sameopenfile compares file tuples, which
is exposed as os.path.sameopenfile.

Rather than list out the three signals (or more over time), the message was
made less specific but still descriptive.

in response to the original checkin.

Move the validation from the original loop into a switch statement,
and adjust a platform check in the tests.

e.g. the pure Python implementation in _pyio).

algorithms_avaiable that respectively list the names of hash algorithms
guaranteed to exist in all Python implementations and the names of hash
algorithms available in the current process.

Renames the attribute new in 3.2a0 'algorithms' to 'algorithms_guaranteed'.

unsupported operation is attempted (for example, writing to a file open
only for reading).