Python-bugzilla

- Use soon-to-be-required Authorization header for RH bugzilla
- Remove cookie auth support

- Detect bugzilla.stage.redhat.com as RHBugzilla
- Add limit as option to build_query (Ivan Lausuch)

- Fix API key leaking into requests exceptions

- Skip man page generation to fix build on Windows (Alexander Todorov)

- Drop python2 support
- New option `bugzilla modify --minor-update option`
- requests: use PYTHONBUGZILLA_REQUESTS_TIMEOUT env variable
- xmlrpc: Don't add api key to passed in user dictionary

- cli: Add query --extrafield, --includefield, --excludefield
- Revive bugzilla.rhbugzilla.RHBugzilla import path