Errata-tool

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* Drop the client-side check to make sure advisory was NEW_FILES before it
would attempt to change anything.

This appears to be a legacy check that is no longer needed. We now let the
Errata Tool return server-side errors if an update is not allowed.

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* connector: Fix logic causing extraneous tracebacks on PUT/POST

* Allow setting to REL_PREP state

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* Add errata call timings (see ``ErrataConnector.debug`` and
``ErrataConnector.timings`` documentation in README)

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* Add needs_distqa flag checking

* Don't double-add builds (avoids traceback)

* ``ErrataConnector`` is now a proper new-style class, to make it easier to
inherit with child classes.

* packaging: ``setup.py bump`` now takes a --version flag, to make it easier to
adopt semver

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* New internal method you may want to override in a subclass:
``Erratum._check_bugs()``

* If an advisory is an RHSA, the ``current_flags`` attribute can contain
either ``request_security`` or ``needs_security``.

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* Remove extra print from ``errataum.addBuildsDirect()``