message: Default session manager loop to None
diff: @@ -17,7 +17,7 @@ VALID_STATES = set(
  class SessionManager(object):
  - def __init__(self, loop, filters=[
  + def __init__(self, loop=None, filters=[
  'add-command',
  'session.state.change']):
  self.notifications = Notifications(loop=loop, filters=filters)
  