catch all exceptions

application.rb

#catch all exceptions  
  unless Rails.application.config.consider_all_requests_local
    rescue_from Exception, with: :render_500
    rescue_from ActionController::RoutingError, with: :render_404
    rescue_from ActionController::UnknownController, with: :render_404
    rescue_from ActionController::UnknownAction, with: :render_404
    rescue_from ActiveRecord::RecordNotFound, with: :render_404
  end

  private
  #generate json messages:
  def render_404(exception)
    render :json => exception.message
  end
  def render_500(exception)
    render :json => exception.message
  end