Fix Jenkins translation jobs

The job glance-propose-translation-update
does not update from
transifex since our po files contain duplicate entries where
obsolete entries duplicate normal entries.

Remove all obsolete entries to fix the job.

Add test to pep8 that checks that no new breakages get
introduced.

Change-Id: I1bae1c1bf27bf664b24cf75fc96efb0fcfddc392
Closes-Bug: #1299349
Catch loading failures if transport_url is not set

The current implementation always tries to get a transport from
oslo.messaging assuming the transport_url option has been set. This is
done to keep backwards compatibility. However, since the default
`rpc_backend` is rabbit, it'll always try to load such driver. The
problem raises when `kombu` is not installed and the `notifier_strategy`
is set to qpid. This will make glance-api fail because it'll try to load
the rabbit driver *before* loading the qpid one.

This patch puts the first load attempt in a try / except block. The
error caught (if any) will be re-raised *just* if transport_url has been
configured, otherwise it'll move forward and try to load the notifier
driver using the old configuration options.

The patch also removes an obsolete test.

Change-Id: I00e653704463ea8245e2960050e0d5e6839f278a
Closes-bug: #1302661
Merge "Catch loading failures if transport_url is not set"
Merge "Fix Jenkins translation jobs"