code: def _execute(self, handler, *args, **kwargs):
          
          # difference to Axel Events: we don't use a timeout and execute all handlers in same thread
          # FIXME: =>possible problem:
          #                       blocking of event firing when user gives a long- or infinitly-running callback function
          # (in Python it doesn't seem possible to forcefully kill a thread with clean ressource releasing,
          #  a thread has to cooperate und behave nice...
          #  execution and killing a process would be possible, but has data corruption problems with queues
          #  and possible interprocess communication problems with given handler/callback function)
  
          result = None
          exc_info = None
  
          try:
              result = handler(*args, **kwargs)
          except Exception:
              exc_info = sys.exc_info()
          if exc_info:
              return exc_info
          return result
docs: executes one callback function