Use compat.WeakMethod in clock.py
@@ -120,11 +120,7 @@ from operator import attrgetter
from heapq import heappush, heappop, heappushpop
from collections import deque
import inspect
-import sys
-if sys.version_info < (3, 4):
from .compat import WeakMethod
-else:
- from weakref import WeakMethod
import pyglet.lib
from pyglet import compat_platform
