code: def get_xauth_access_token(self, username, password):
          
          try:
              url = self._get_oauth_url('access_token')
              oauth = OAuth1(self.consumer_key,
                             client_secret=self.consumer_secret)
              r = requests.post(url=url,
                                auth=oauth,
                                headers={'x_auth_mode': 'client_auth',
                                         'x_auth_username': username,
                                         'x_auth_password': password})
  
              credentials = parse_qs(r.content)
              return credentials.get('oauth_token')[0], credentials.get('oauth_token_secret')[0]
          except Exception as e:
              raise TweepError(e)
docs: Get an access token from an username and password combination.
          In order to get this working you need to create an app at
          http://twitter.com/apps, after that send a mail to api@twitter.com
          and request activation of xAuth for it.