Don't attempt to index users before a Review Board site is fully set up.

Review Request #10700 — Created Sept. 7, 2019 and submitted — Latest diff uploaded

Review Board

Our Haystack signal processor listens for newly-saved users and, if
search indexing is enabled, adds them to the index. The problem is,
the act of checking if they're enabled (looking up a
SiteConfiguration) can fail when creating a new database with a
superuser for the first time.

The reason this happens is that django.contrib.auth will prompt the
admin to create a superuser in response to the post_syncdb or
post_migrate signal the first time that the User model is added to
the database. This occurs before django.contrib.sites has a chance to
create its Site object. Normally that's fine, but our signal processor
is getting in the way by operating on that new superuser and accessing
the not-yet-created Site.

This wasn't a problem in the past because we used to shell out to the
syncdb command, which never invoked the code that registers our signal
processor. A recent change removed that in favor of directly interfacing
with the Django Evolution Evolver class, meaning that the process is
now taking place in an environment where the signal processor is

This change updates the signal processor to check whether we have the
right entries in the database before handling each signal. This fixes

Unit tests pass.

Successfully ran for the first time with a superuser,
and saw that the database populated correctly.