Fixed #23895 -- Prevented pickling of ResolverMatch.

Pickling a ResolverMatch did not work correctly in many cases,
especially with CBVs and URLResolvers in the list of tried URL paths.

AUTHORS

@@ -478,6 +478,7 @@ answer newbie questions, and generally made Django that much better:
     Jökull Sólberg Auðunsson <[email protected]>
     Jon Dufresne <[email protected]>
     Jonas Haag <[email protected]>
+    Jonathan Davis <[email protected]>
     Jonatas C. D. <[email protected]>
     Jonathan Buchanan <[email protected]>
     Jonathan Daugherty (cygnus) <http://www.cprogrammer.org/>

django/urls/resolvers.py

@@ -10,6 +10,7 @@
 import re
 import string
 from importlib import import_module
+from pickle import PicklingError
 from urllib.parse import quote
 
 from asgiref.local import Local
@@ -71,6 +72,9 @@ def __repr__(self):
             )
         )
 
+    def __reduce_ex__(self, protocol):
+        raise PicklingError(f'Cannot pickle {self.__class__.__qualname__}.')
+
 
 def get_resolver(urlconf=None):
     if urlconf is None:

tests/urlpatterns_reverse/tests.py

@@ -1,6 +1,7 @@
 """
 Unit tests for reverse URL lookups.
 """
+import pickle
 import sys
 import threading
 
@@ -1167,6 +1168,12 @@ def test_repr_functools_partial(self):
                     f"route='{name}/')",
                 )
 
+    @override_settings(ROOT_URLCONF='urlpatterns.path_urls')
+    def test_pickling(self):
+        msg = 'Cannot pickle ResolverMatch.'
+        with self.assertRaisesMessage(pickle.PicklingError, msg):
+            pickle.dumps(resolve('/users/'))
+
 
 @override_settings(ROOT_URLCONF='urlpatterns_reverse.erroneous_urls')
 class ErroneousViewTests(SimpleTestCase):