[2.2.x] Fixed #31654 -- Fixed cache key validation messages.

Backport of 926148ef01 from master.

django/core/cache/backends/base.py

@@ -287,6 +287,6 @@ def memcache_key_warnings(key):
         if ord(char) < 33 or ord(char) == 127:
             yield (
                 'Cache key contains characters that will cause errors if '
-                'used with memcached: %r' % key, CacheKeyWarning
+                'used with memcached: %r' % key
             )
             break

docs/releases/2.2.14.txt

@@ -0,0 +1,13 @@
+===========================
+Django 2.2.14 release notes
+===========================
+
+*Expected July 1, 2020*
+
+Django 2.2.14 fixes a bug in 2.2.13.
+
+Bugfixes
+========
+
+* Fixed messages of ``InvalidCacheKey`` exceptions and ``CacheKeyWarning``
+  warnings raised by cache key validation (:ticket:`31654`).

docs/releases/index.txt

@@ -25,6 +25,7 @@ versions of the documentation contain the release notes for any later releases.
 .. toctree::
    :maxdepth: 1
 
+   2.2.14
    2.2.13
    2.2.12
    2.2.11

tests/cache/tests.py

@@ -619,8 +619,9 @@ class BaseCacheTests:
         cache.key_func = func
 
         try:
-            with self.assertWarnsMessage(CacheKeyWarning, expected_warning):
+            with self.assertWarns(CacheKeyWarning) as cm:
                 cache.set(key, 'value')
+            self.assertEqual(str(cm.warning), expected_warning)
         finally:
             cache.key_func = old_func
 
@@ -1257,8 +1258,9 @@ class BaseMemcachedTests(BaseCacheTests):
         invalid key.
         """
         msg = expected_warning.replace(key, cache.make_key(key))
-        with self.assertRaisesMessage(InvalidCacheKey, msg):
+        with self.assertRaises(InvalidCacheKey) as cm:
             cache.set(key, 'value')
+        self.assertEqual(str(cm.exception), msg)
 
     def test_default_never_expiring_timeout(self):
         # Regression test for #22845