Twitter - get authorization URL

    def get_request_token(self, callback_url):
        """ Get request token. 
        Request token will be used to construct authorization URL later.
        
        Args:
            callback_url - basestring, not urlencoded. 
            Example: http://entrecard.com/oauth/callback
        
        Returns:
            request_token of type oauth2.Token
            or
            None if request token was not received from server
            
        Raises:
            -

        """
        parameters = dict(oauth_consumer_key = self.consumer.key,
                          oauth_signature_method = self.signature_method.name,
                          oauth_callback = callback_url,
                          oauth_timestamp = str(int(time.time())),
                          oauth_nonce = str(int(time.time())))
        oauth_request = oauth2.Request(method = 'GET', 
                                       url=self.request_url, 
                                       parameters = parameters)
        oauth_request.sign_request(self.signature_method, self.consumer, None)
        url_params = urllib.urlencode(oauth_request)
        response = self.read_response(self.request_url, url_params)
        response_dict = self.validate_keys(response, ['oauth_token', 'oauth_token_secret'])
        if response_dict:
            return oauth2.Token(response_dict["oauth_token"], response_dict["oauth_token_secret"])

    def get_authorization_url(self, callback_url):
        """ Gets request token from server and composes authorization URL using 
        request token
        
        Returns:
            authorization_url (basestring) - URL, which is used in step 2 of workflow 
            (see docstring for parent class)
            OR
            None if request token was not obtained.
        
        """
        request_token = self.get_request_token(callback_url)
        if request_token:
            oauth_request = oauth2.Request.from_consumer_and_token(
                self.consumer, 
                token = request_token, 
                http_url = self.authorization_url)
            oauth_request.sign_request(self.signature_method, self.consumer, request_token)
            # User will be redirected to this URL
            return '%s?%s' % (self.authorization_url, urllib.urlencode(oauth_request))