Fixed so 'get_source_files()' calls 'check_extension_list()' -- that way, we can run "sdist" on a distribution with old-style extension structures even if we haven't built it yet.  Bug spotted by Harry Gebel.
Fixed so 'get_source_files()' calls 'check_extension_list()' -- that way,
we can run "sdist" on a distribution with old-style extension structures
even if we haven't built it yet.  Bug spotted by Harry Gebel.

pypa/setuptools,pypa/setuptools,pypa/setuptools