Fixed #26520 -- Fixed a regression where SessionBase.pop() didn't return a KeyError.

django/contrib/sessions/backends/base.py

@@ -42,6 +42,8 @@ class SessionBase(object):
     TEST_COOKIE_NAME = 'testcookie'
     TEST_COOKIE_VALUE = 'worked'
 
+    __not_given = object()
+
     def __init__(self, session_key=None):
         self._session_key = session_key
         self.accessed = False
@@ -65,9 +67,10 @@ class SessionBase(object):
     def get(self, key, default=None):
         return self._session.get(key, default)
 
-    def pop(self, key, default=None):
+    def pop(self, key, default=__not_given):
         self.modified = self.modified or key in self._session
-        return self._session.pop(key, default)
+        args = () if default is self.__not_given else (default,)
+        return self._session.pop(key, *args)
 
     def setdefault(self, key, value):
         if key in self._session:

docs/releases/1.9.6.txt

@@ -18,3 +18,6 @@ Bugfixes
 
 * Prevented ``makemigrations`` from generating infinite migrations for a model
   field that references a ``functools.partial`` (:ticket:`26475`).
+
+* Fixed a regression where ``SessionBase.pop()`` returned ``None`` rather than
+  raising a ``KeyError`` for nonexistent values (:ticket:`26520`).

docs/topics/http/sessions.txt

@@ -205,7 +205,7 @@ You can edit it multiple times.
 
       Example: ``fav_color = request.session.get('fav_color', 'red')``
 
-    .. method:: pop(key, default=None)
+    .. method:: pop(key, default=__not_given)
 
       Example: ``fav_color = request.session.pop('fav_color', 'blue')``
 

tests/sessions_tests/tests.py

@@ -88,6 +88,10 @@ class SessionTestsMixin(object):
         self.assertTrue(self.session.accessed)
         self.assertFalse(self.session.modified)
 
+    def test_pop_no_default_keyerror_raised(self):
+        with self.assertRaises(KeyError):
+            self.session.pop('some key')
+
     def test_setdefault(self):
         self.assertEqual(self.session.setdefault('foo', 'bar'), 'bar')
         self.assertEqual(self.session.setdefault('foo', 'baz'), 'bar')