Update priority enum for Taillight >= 0.4.

--- py3-pyirc-3.0b1_git20190929/PyIRC/signal.py.old	2019-09-29 17:01:50.000000000 +0000
+++ py3-pyirc-3.0b1_git20190929/PyIRC/signal.py	2022-12-04 00:44:03.697227554 +0000
@@ -12,14 +12,14 @@
 from inspect import getmembers
 from logging import getLogger
 
-from taillight.signal import UnsharedSignal
+from taillight.signal import SignalPriority, UnsharedSignal
 from taillight import ANY
 
 
 _logger = getLogger(__name__)  # pylint: disable=invalid-name
 
 
-def event(hclass, event_name, priority=UnsharedSignal.PRIORITY_NORMAL,
+def event(hclass, event_name, priority=SignalPriority.PRIORITY_NORMAL,
           listener=ANY):
     """Tag a function as an event for later binding.