docs: def user_exists(username,
                  token_manager=None,
                  app_url=defaults.APP_URL):
      """
      check if the user exists with the specified username
  
      """
      headers = token_manager.get_access_token_headers()
      auth_url = environment.get_auth_url(app_url=app_url)
      url = "%s/api/v1/accounts?username=%s" % (auth_url, username)
      response = requests.get(url, headers=headers)
  
      if response.status_code == 404:
          return False
      elif response.status_code == 200:
          return True
      else:
          raise JutException('Error %s: %s' % (response.status_code, response.text))