iopath fails to build on Windows 3.8

[vedanuj]

We are using iopath in MMF library. Our CI tests are failing with this error from iopath library on Windows, Python 3.8 :

c:\miniconda\envs\mmf\lib\site-packages\iopath\common\file_io.py:14: in <module>
    import portalocker  # type: ignore
c:\miniconda\envs\mmf\lib\site-packages\portalocker\__init__.py:4: in <module>
    from . import portalocker
c:\miniconda\envs\mmf\lib\site-packages\portalocker\portalocker.py:11: in <module>
    import win32file
E   ImportError: DLL load failed while importing win32file: The specified module could not be found.

[sujitoc]

Thanks @vedanuj for reporting this issue. We weren't planning to support windows, but I guess we should since MMF depends on it. Do you have any quick fix suggestions?