python/aqmp: add QMP event support

This class was designed as a "mix-in" primarily so that the feature
could be given its own treatment in its own python module.

It gets quite a bit too long otherwise.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 20210915162955.333025-16-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/qemu/aqmp/__init__.py

@@ -22,6 +22,7 @@ managing QMP events.
 # the COPYING file in the top-level directory.
 
 from .error import AQMPError
+from .events import EventListener
 from .message import Message
 from .protocol import ConnectError, Runstate, StateError
 
@@ -30,6 +31,7 @@ from .protocol import ConnectError, Runstate, StateError
 __all__ = (
     # Classes, most to least important
     'Message',
+    'EventListener',
     'Runstate',
 
     # Exceptions, most generic to most explicit