Buildbot jobs fail intermittently with "exceptions.Exception: Actual commit (…) differs from requested commit (…)" #18338
Description
This is happening a lot lately. As in, every PR needs to be retried multiple times. CC @edunham @larsbergstrom @Manishearth
Example:
http://build.servo.org/builders/mac-rel-wpt1/builds/5713
err.text:
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1445, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1299, in _inlineCallbacks
result = g.send(result)
File "/usr/local/lib/python2.7/dist-packages/buildbot/process/buildstep.py", line 322, in startStep
result = yield self.run()
File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1445, in unwindGenerator
return _inlineCallbacks(None, gen, Deferred())
--- <exception caught here> ---
File "/usr/local/lib/python2.7/dist-packages/twisted/internet/defer.py", line 1299, in _inlineCallbacks
result = g.send(result)
File "factories.py", line 39, in run
got_rev, rev
exceptions.Exception: Actual commit (c6758e38ff77f706dd6cc2edc19854b03b285491) differs from requested commit (8c12d5bbc433aedb486b541ca925dd4065864aba)