[Regression]: EventEmitter.listeners("foo") throws if no listener exists

[mxschmitt]

The following:

from pyee import EventEmitter
ee = EventEmitter()
ee.listeners("foo")

results in:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/.../env/lib/python3.10/site-packages/pyee/base.py", line 229, in listeners
    return list(self._events[event].keys())
KeyError: 'foo'
>>> 

since version 9.0.0. In version <8 it was returning an empty list instead. This most likely broke in #99 when the defaultdict of EventEmitter._events got changed to a normal dict.

[jfhbrook]

Yeah, sounds like a regression. I'll patch shortly.

[jfhbrook]

Released your patch as 9.0.1 - thanks so much!!