[py3] Avoided the deprecated base64 interface.

This fixes a deprecation warning under Python 3.

django/contrib/sessions/backends/base.py

@@ -81,10 +81,10 @@ def encode(self, session_dict):
         "Returns the given session dictionary pickled and encoded as a string."
         pickled = pickle.dumps(session_dict, pickle.HIGHEST_PROTOCOL)
         hash = self._hash(pickled)
-        return base64.encodestring(hash.encode() + b":" + pickled)
+        return base64.b64encode(hash.encode() + b":" + pickled)
 
     def decode(self, session_data):
-        encoded_data = base64.decodestring(smart_bytes(session_data))
+        encoded_data = base64.b64decode(smart_bytes(session_data))
         try:
             # could produce ValueError if there is no ':'
             hash, pickled = encoded_data.split(b':', 1)

django/core/cache/backends/db.py

@@ -72,7 +72,7 @@ def get(self, key, default=None, version=None):
             transaction.commit_unless_managed(using=db)
             return default
         value = connections[db].ops.process_clob(row[1])
-        return pickle.loads(base64.decodestring(value))
+        return pickle.loads(base64.b64decode(value))
 
     def set(self, key, value, timeout=None, version=None):
         key = self.make_key(key, version=version)
@@ -103,7 +103,7 @@ def _base_set(self, mode, key, value, timeout=None):
         if num > self._max_entries:
             self._cull(db, cursor, now)
         pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
-        encoded = base64.encodestring(pickled).strip()
+        encoded = base64.b64encode(pickled).strip()
         cursor.execute("SELECT cache_key, expires FROM %s "
                        "WHERE cache_key = %%s" % table, [key])
         try: