In commit 5d1ff6bd I added some logic to
relcache.c to try to ensure that the regression tests would fail if we
made a mistake about which relations belong in the relcache init files.
I'm quite sure I tested that, but I must have done so only for the
non-shared-catalog case, because a report from Adam Brightwell showed that
the regression tests still pass just fine if we bollix the shared-catalog
init file in the way this code was supposed to catch.  The reason is that
that file gets loaded before we do client authentication, so the WARNING
is not sent to the client, only to the postmaster log, where it's far too
easily missed.

The least Rube Goldbergian answer to this is to put an Assert(false)
after the elog(WARNING).  That will certainly get developers' attention,
while not breaking production builds' ability to recover from corner
cases with similar symptoms.

Since this is only of interest to developers, there seems no need for
a back-patch, even though the previous commit went into all branches.