Issue 3498: mod_cls - Python tracker

Using sphinx I get the following error if I want to document methods via
automethod:

reading sources... copyright glossary [..] refbrowser Exception
occurred: File
  "[..]/doctools/sphinx/ext/autodoc.py", line 313, in resolve_name
    if not mod_cls:
UnboundLocalError: local variable 'mod_cls' referenced before
assignment. [..]

I am not familiar with the code base, but from the comments the attached
patch should address the issue.