Docker language fails on Windows - os.getuid()

[cz-fish]

docker_cmd in languages/docker.py uses os.getuid() and os.getgid() that don't exist in Python on Windows.

A hook that uses Docker on Windows fails to execute with

An unexpected error has occurred: AttributeError: module 'os' has no attribute 'getuid'
Traceback (most recent call last):
  File "C:\Python36\lib\site-packages\pre_commit\error_handler.py", line 46, in error_handler
    yield
  File "C:\Python36\lib\site-packages\pre_commit\main.py", line 294, in main
    return run(args.config, store, args)
  File "C:\Python36\lib\site-packages\pre_commit\commands\run.py", line 293, in run
    return _run_hooks(config, hooks, args, environ)
  File "C:\Python36\lib\site-packages\pre_commit\commands\run.py", line 214, in _run_hooks
    retval |= _run_single_hook(classifier, hook, args, skips, cols)
  File "C:\Python36\lib\site-packages\pre_commit\commands\run.py", line 124, in _run_single_hook
    tuple(filenames) if hook.pass_filenames else (),
  File "C:\Python36\lib\site-packages\pre_commit\repository.py", line 100, in run
    return lang.run_hook(self, file_args)
  File "C:\Python36\lib\site-packages\pre_commit\languages\docker.py", line 99, in run_hook
    cmd = docker_cmd() + entry_tag + cmd_rest
  File "C:\Python36\lib\site-packages\pre_commit\languages\docker.py", line 80, in docker_cmd
    '-u', '{}:{}'.format(os.getuid(), os.getgid()),
AttributeError: module 'os' has no attribute 'getuid'

The same hook works fine in Windows Subsystem for Linux.

[asottile]

makes sense, I haven't been able to get testing for docker on windows set up just yet -- not sure what the right thing to put for that argument is to be honest. The current support suggests only macos and linux for now

I'd be open to a patch if you'd like to get one working!