Portainer can sometimes hang when certain types of scheduler errors are thrown

[tarnfeld]

Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 551, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 504, in run
    self.__target(*self.__args, **self.__kwargs)
  File "portainer/app/scheduler.py", line 172, in _handle_offers
    mem=mem
  File "portainer/app/scheduler.py", line 327, in _prepare_task
    raise ValueError("No REPOSITORY given for %s", path)
ValueError: ('No REPOSITORY given for %s', '/opt/.../Dockerfile')