> Here is a patch for import.c.

Looks good to me.

> This new patch also fixes importlib.

"""
                path_tmp = path + '.tmp'
                with _io.FileIO(path_tmp, 'wb') as file:
                    file.write(data)
                _os.rename(path_tmp, path)
"""

I don't know exactly the context in which this code runs, but you can have a corruption if multiple processes try to write the bytecode file at the same time, since they'll all open the .tmp file: it should be opened with O_EXCL.

Also, as a side note, I'm wondering whether this type of check:
"""
            if not sys.platform.startswith('win'):
                # On POSIX-like platforms, renaming is atomic
"""

couldn't be rewritten as
"""
            if os.name == 'posix':
                # On POSIX-like platforms, renaming is atomic
"""

Fox example, does OS-X report as POSIX?