AuthenticationBackend not working about django-cassandra-engine HOT 5 OPEN

class SessionStore(SessionBase):
    """
    A Cassandra based session store.
    """
    def load(self):
        try:
            #GET SESSIONDATA BASED ON SESSIONKEY
            data = cass.get_session(self.session_key)
            #NOW
            a = datetime.now()
            #EXPIRE-DATE - NOW = TIME-LEFT
            c = data['expire_date'] - a
            if c.total_seconds() > 0:
                return self.decode(force_unicode(data['session_data']))
            #Manually remove session from DB
            cass.remove_session(session_key)
            self._session_key = None
            return {}
        except cass.DatabaseError:
            self._session_key = None
            return {}

    def create(self):
        while True:
            self._session_key = self._get_new_session_key()
            try:
                # Save immediately to ensure we have a unique entry in the database
                self.save(must_create=True)
            except CreateError:
                # Key wasn't unique. Try again.
                continue
            self.modified = True
            return

    def save(self, must_create=False):
        if self.session_key is None:
            return self.create()

        if must_create and self.exists(self.session_key):
            raise CreateError
        else:
            #DJANGO GENERATES NEW SESSION_DATA
            session_data = self.encode(self._get_session(no_load=must_create))
            #NOW + EXPIRY SECONDS = EXPIRE-DATE
            expire_date = datetime.now() + timedelta(seconds=self.get_expiry_age())
            #STRIP MICROSECONDS
            expire_date = expire_date.strftime("%Y-%m-%d %H:%M:%S")
            #ADD TIMEZONE
            expire_date = expire_date + '+0000'

            cass.create_session(self.session_key, session_data, expire_date)

    def exists(self, session_key):
        #CHECK IF SESSION_KEY EXISTS...
        return cass.check_session_existence(session_key)

    def delete(self, session_key=None):
        if session_key is None:
            if self.session_key is None:
                return
            session_key = self.session_key
        cass.remove_session(session_key)

# EXCEPTIONS
class DatabaseError(Exception):
    """
    The base error that functions in this module will raise when things go
    wrong.
    """
    pass
class NotFound(DatabaseError): pass
class InvalidDictionary(DatabaseError): pass

#COOKIES SESSION OPERATIONS
def create_session(session_key, session_data, expire_date):
    cursor.execute("INSERT INTO sessions (session_key, session_data, expire_date) VALUES ('%s', '%s', '%s')" % (session_key, session_data, expire_date));
    return True

def check_session_existence(session_key):
    result = cursor.execute("SELECT session_key FROM sessions WHERE session_key = '%s'" % session_key);
    if not result:
        return False
    return True

def remove_session(session_key):
    cursor.execute("DELETE FROM sessions WHERE session_key = '%s'" % session_key);
    return True

def get_session(session_key):
    result = cursor.execute("SELECT session_data, expire_date FROM sessions WHERE session_key = '%s'" % session_key);
    if not result:
        raise DatabaseError()
    return result[0]