beta: monitor fatal errors on beta labs

We discussed doing this at the quarterly review:

https://www.mediawiki.org/wiki/Wikimedia_Release_and_QA_Team/Quarterly_review,_November_2013

This script is intended to run each hour.  In its current form it could
be started as a cron job.  Alternately, we could have it loop and sleep
for seconds_since_last_run while running in a screen() session.

I tested this by running it on deployment-bastion and sending
messages to myself, and it works nicely.

Script has been imported by Antoine from the qa/browsertests repository
so it can be puppetized.  Originally submitted as:
  https://gerrit.wikimedia.org/r/#/c/105715/

bug: 60046
Change-Id: I0498bb87dd3cb239ea08d521ddf285faea9cffee