AssertionError: Build target not found

[La0]

https://sentry.prod.mozaws.net/operations/code-review-bot/issues/6358889/

AssertionError: Build target not found
(1 additional frame(s) were not displayed)
...
  File "python3.7/contextlib.py", line 74, in inner
    return func(*args, **kwds)
  File "code_review_bot/cli.py", line 99, in main
    update_build=phabricator_reporting_enabled,
  File "code_review_bot/revisions.py", line 87, in __init__
    self.load_phabricator(try_task)
  File "code_review_bot/revisions.py", line 123, in load_phabricator
    buildable = self.api.find_target_buildable(self.build_target_phid)
  File "libmozdata/phabricator.py", line 460, in find_target_buildable
    assert len(targets) == 1, "Build target not found"

AssertionError: Build target not found

I think this issue happens a lot on testing only, because the testing hook is triggered for pulse messages from prod. But it's currently connected to the phab-dev instance (which does not have the requested build).

Cleanly failing the task with a specific exception + log should do the trick.