py3: convert os.__file__ to bytes

os.__file__ returns unicode path on Python 3. We need to have bytespath. This
patch uses pycompat.fsencode() to encode unicode path to bytes path.

mercurial/commands.py

@@ -1903,7 +1903,7 b' def debuginstall(ui, **opts):'
     fm.write('pythonver', _("checking Python version (%s)\n"),
              ("%d.%d.%d" % sys.version_info[:3]))
     fm.write('pythonlib', _("checking Python lib (%s)...\n"),
-             os.path.dirname(os.__file__))
+             os.path.dirname(pycompat.fsencode(os.__file__)))
 
     security = set(sslutil.supportedprotocols)
     if sslutil.hassni: