generates a request token

def _request_token(self, method, client):
        '''
        generates a request token
        '''
        if time.time() - self.session.time > grooveshark.const.TOKEN_TIMEOUT:
            self._get_token()
        random_value = self._random_hex()
        return random_value + hashlib.sha1((method + ':' + self.session.token + ':' + grooveshark.const.CLIENTS[client]['token'] + ':' + random_value).encode('utf-8')).hexdigest()