docs: def authenticate(self):
          """Authenticate the session"""
          postdata = self.authentication_postdata
          jar = requests.cookies.cookielib.CookieJar()
          self.cookies = jar
          resp = self.get(self.authentication_base_url)
          authtok = _extract_authenticity_token(resp.content)
          if postdata is None:
              # This works for GitHub
              postdata = {"login": self.oauth2_username,
                          "password": self._oauth2_password,
                          "authenticity_token": authtok,
                          "commit": "Sign+in",
                          "utf8": u"\u2713",
                          }  # pylint: disable=bad-continuation
              self.authentication_postdata = postdata
          if self.authentication_session_url is None:
              # This is also for GitHub
              authentication_session_url = "https://github.com/session"
              self.authentication_session_url = authentication_session_url
          self.post(self.authentication_session_url, data=postdata)