D3631: py3: use pycompat.fsencode to convert path to bytes

[Yuya Nishihara]

> --- a/contrib/hg-ssh
> +++ b/contrib/hg-ssh
> @@ -39,6 +39,7 @@
>  
>  from mercurial import (
>      dispatch,
> +    pycompat,
>      ui as uimod,
>  )
>  
> @@ -69,7 +70,7 @@
>          path = cmdargv[2]
>          repo = os.path.normpath(os.path.join(cwd, os.path.expanduser(path)))
>          if repo in allowed_paths:
> -            cmd = [b'-R', repo, b'serve', b'--stdio']
> +            cmd = [b'-R', pycompat.fsencode(repo), b'serve', b'--stdio']

It's probably better to convert sys.argv and cwd to bytes. Otherwise we'll
have to be a human type checker.