The TOM Toolkit offers a few custom exceptions that are documented in the API documentation, but one in particular should be noted.
For any modules exposing external services, such as brokers, harvesters, or facilities, a failed authentication should
ImproperCredentialsException. Exceptions of this type are caught by the TOM Toolkit’s built-in
ExternalServiceMiddleware. This middleware will display an error at the top of the page and redirect the user to the