See these two runs:
https://uberchromegw.corp.google.com/i/chromeos/builders/master-paladin/builds/16835
https://uberchromegw.corp.google.com/i/chromeos/builders/master-paladin/builds/16834

There were no CLs in the CQ run, and it failed with the "KeyError: u'beaglebone-paladin'".

1. The error message doesn't really tell anything about what's going on
2. A CQ run with no CLs (and no bugs in the tree) should be green.