Index: contrib/sessions/middleware.py
===================================================================
--- contrib/sessions/middleware.py	(revision 4872)
+++ contrib/sessions/middleware.py	(working copy)
@@ -68,10 +68,21 @@
     _session = property(_get_session)
 
 class SessionMiddleware(object):
+    def __init__(self):
+        self.exception_occured = False
+
     def process_request(self, request):
         request.session = SessionWrapper(request.COOKIES.get(settings.SESSION_COOKIE_NAME, None))
 
+    def process_exception(self, request, exception):
+        self.exception_occured = True
+
     def process_response(self, request, response):
+        # Don't try to save session when process method raised an exception. In case of database exceptions
+        # it may not even be possible. See ticket #3881.
+        if self.exception_occured:
+            return response
+
         # If request.session was modified, or if response.session was set, save
         # those changes and set a session cookie.
         try: