Adapt resolution of classes from importlib.machinery. Restores compatibility for PyPy3 where importlib.machinery exists but FileFinder and SourceFileLoader aren't implemented.
Adapt resolution of classes from importlib.machinery. Restores compatibility for PyPy3 where importlib.machinery exists but FileFinder and SourceFileLoader aren't implemented.

pypa/setuptools,pypa/setuptools,pypa/setuptools