Disabled consumer subclasses crash at startup

[abompard]

When starting fedmsg-hub I get this in my console:

[    fedmsg    INFO] * disabled by config - fmn.consumer.consumer:FMNConsumer
[moksha.hub   ERROR] Failed to init <class 'fmn.consumer.consumer.FMNConsumer'> consumer.
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/moksha/hub/hub.py", line 407, in __init_consumers
    c = c_class(self)
  File "/usr/lib/python2.7/site-packages/fmn/consumer/consumer.py", line 65, in __init__
    self.uri = self.hub.config.get('fmn.sqlalchemy.uri', None)
AttributeError: 'FMNConsumer' object has no attribute 'hub'

I found the reason: on line 105 of the consumers/__init__.py file a check is made to enable the instance or not. If not, the init method is aborted before calling the superclass' constructor method. But it's this superclass' constructor that sets self.hub to the hub provided as argument.
As a result, if the subclass tries to use self.hub later in its constructor, it will crash.