def mark_read(self, user):
    token = os.getenv(TOKEN_NAME)
    if not token:
      raise ValueError(("Environment variable {0} needs to be set to a GitHub "
                        "token.").format(token))
    client = github3.GitHub(username=user, token=token)
    notifications = client.notifications()

    # https://developer.github.com/v3/activity/notifications/
    #
    # How do we identify closed pull requests?
    for n in notifications:
      process_notification(n)