[1.1.X] Corrected merge of r12411 to 1.1.X branch (see r12415).

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@12416 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/cache/backends/db.py

@@ -81,7 +81,8 @@ def delete(self, key):
     def has_key(self, key):
         now = datetime.now().replace(microsecond=0)
         cursor = connection.cursor()
-        cursor.execute("SELECT cache_key FROM %s WHERE cache_key = %%s and expires > %%s" % self._table, [key, now])
+        cursor.execute("SELECT cache_key FROM %s WHERE cache_key = %%s and expires > %%s" % self._table,
+                        [key, connection.ops.value_to_db_datetime(now)])
         return cursor.fetchone() is not None
 
     def _cull(self, cursor, now):