chore: fix python lint warnings (#14638)

* chore: fix lint warnings

* chore: another try at python import errors

Looks like the problem is that dbus_mock.py is running as
a script but living in the `lib/` directory where it's part of a
module. Moving it up into the `script/` directory seems to
solve the issue.

script/bump-version.py

@@ -80,7 +80,7 @@ def main():
   else:
     raise Exception("Invalid current version: " + curr_version)
 
-  if args.new_version == None and args.bump == None and args.stable == False:
+  if args.new_version is None and args.bump is None and not args.stable:
     parser.print_help()
     return 1