Randomly travis brought this up:

Traceback (most recent call last):
  File "/var/lib/buildbot/workers/default/travis_bionic/build/src/bitmessageqt/tests/main.py", line 34, in tearDown
    self.fail('Exception in the main thread: %s' % exc)
AssertionError: Exception in the main thread: TCPConnection instance has no attribute 'userAgent'

I looked and TCPConnection.userAgent isn't initialised in __init__, only later.