Reduce warnings

[klahnakoski]

There are too many warnings while running in prod. Each warning sends an email.

ip-172-31-1-12 (pid 8972) - 2018-05-05 11:53:38 - Main Thread - "service.py:784" (get_tuids) - WARNING: xpcom/ds/nsArrayUtils.h does not exist in the revision 334aed1c3232

Warning are for unusual situations that the machine can handle, but really should be fixed.

[klahnakoski]

Turns out these particular warnings are good: HG is suspicious of 404s, so reducing the cause will reduce the number of 404s and the number of warnings.