class Slack::Web::Faraday::Response::RaiseError

def on_complete(env)
  raise Slack::Web::Api::Errors::TooManyRequestsError, env.response if env.status == 429
  return unless env.success?
  body = env.body
  return unless body
  return if body['ok']
  error_message = body['error'] || body['errors'].map { |message| message['error'] }.join(',')
  error_class = Slack::Web::Api::Errors::ERROR_CLASSES[error_message]
  error_class ||= Slack::Web::Api::Errors::SlackError
  raise error_class.new(error_message, env.response)
end