ActionDispatch::ShowExceptions

# Action Dispatch ShowExceptions

This middleware rescues any exception returned by the application and calls an exceptions app that will wrap it in a format for the end user.

The exceptions app should be passed as a parameter on initialization of `ShowExceptions`. Every time there is an exception, `ShowExceptions` will store the exception in `env rewrite the `PATH_INFO` to the exception status code, and call the Rack app.

In Rails applications, the exceptions app can be configured with `config.exceptions_app`, which defaults to ActionDispatch::PublicExceptions.

If the application returns a response with the `X-Cascade` header set to `“pass”`, this middleware will send an empty response as a result with the correct status code. If any exception happens inside the exceptions app, this middleware catches the exceptions and returns a failsafe response.