PR#159: Improve the logging related to Errata advisories handling. -

Adds wrappers for log.debug/log.info/log.warn/log.error to BaseHandler class. These wrappers add prefix to logged message based on currently handled event set by `BaseHandler.set_context()".
Implements models.Event.__str__() to return user readable representation of Event which is used in logs.
Removes per-UMB-message debug logging messages, because they create lot of traffic in logs, but we have never used them for anything.

rebased onto 81b3ad9898f75f23965c0f268f4f23ee0e31b435

Dec 15, 2017

Fixed flake8 errors.

s/lot of/ a lot of

:thumbsup:

Looks good for me.

Pull-Request has been merged by jkaluza

Jan 2, 2018