Refs #23919 -- Removed six.PY2/PY3 usage

Thanks Tim Graham for the review.

django/dispatch/dispatcher.py

@@ -2,15 +2,9 @@ import sys
 import threading
 import weakref
 
-from django.utils import six
 from django.utils.inspect import func_accepts_kwargs
 from django.utils.six.moves import range
 
-if six.PY2:
-    from .weakref_backports import WeakMethod
-else:
-    from weakref import WeakMethod
-
 
 def _make_id(target):
     if hasattr(target, '__func__'):
@@ -107,13 +101,10 @@ class Signal(object):
             receiver_object = receiver
             # Check for bound methods
             if hasattr(receiver, '__self__') and hasattr(receiver, '__func__'):
-                ref = WeakMethod
+                ref = weakref.WeakMethod
                 receiver_object = receiver.__self__
-            if six.PY3:
-                receiver = ref(receiver)
-                weakref.finalize(receiver_object, self._remove_receiver)
-            else:
-                receiver = ref(receiver, self._remove_receiver)
+            receiver = ref(receiver)
+            weakref.finalize(receiver_object, self._remove_receiver)
 
         with self.lock:
             self._clear_dead_receivers()

django/dispatch/weakref_backports.py

@@ -1,67 +0,0 @@
-"""
-weakref_backports is a partial backport of the weakref module for python
-versions below 3.4.
-
-Copyright (C) 2013 Python Software Foundation, see LICENSE.python for details.
-
-The following changes were made to the original sources during backporting:
-
- * Added `self` to `super` calls.
- * Removed `from None` when raising exceptions.
-
-"""
-from weakref import ref
-
-
-class WeakMethod(ref):
-    """
-    A custom `weakref.ref` subclass which simulates a weak reference to
-    a bound method, working around the lifetime problem of bound methods.
-    """
-
-    __slots__ = "_func_ref", "_meth_type", "_alive", "__weakref__"
-
-    def __new__(cls, meth, callback=None):
-        try:
-            obj = meth.__self__
-            func = meth.__func__
-        except AttributeError:
-            raise TypeError("argument should be a bound method, not {}"
-                            .format(type(meth)))
-        def _cb(arg):
-            # The self-weakref trick is needed to avoid creating a reference
-            # cycle.
-            self = self_wr()
-            if self._alive:
-                self._alive = False
-                if callback is not None:
-                    callback(self)
-        self = ref.__new__(cls, obj, _cb)
-        self._func_ref = ref(func, _cb)
-        self._meth_type = type(meth)
-        self._alive = True
-        self_wr = ref(self)
-        return self
-
-    def __call__(self):
-        obj = super(WeakMethod, self).__call__()
-        func = self._func_ref()
-        if obj is None or func is None:
-            return None
-        return self._meth_type(func, obj)
-
-    def __eq__(self, other):
-        if isinstance(other, WeakMethod):
-            if not self._alive or not other._alive:
-                return self is other
-            return ref.__eq__(self, other) and self._func_ref == other._func_ref
-        return False
-
-    def __ne__(self, other):
-        if isinstance(other, WeakMethod):
-            if not self._alive or not other._alive:
-                return self is not other
-            return ref.__ne__(self, other) or self._func_ref != other._func_ref
-        return True
-
-    __hash__ = ref.__hash__