Add tests for docstring Validation Script + py27 compat
- [x] closes #xxxx
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@jorisvandenbossche @toobaz a few edits here should make it work for both Py3 and Py2 users