Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

You could add a custom exception handler with `@app.exception_handler()`:

{* ../../docs_src/handling_errors/tutorial003.py hl[5:7,13:18,24] *}

Here, if you request `/unicorns/yolo`, the *path operation* will `raise` a `UnicornException`.

                    // Exception should be caught and logged
                    exceptionHandled.set(true);
                }
            }
        };

        FwAssistantDirector assistantDirector = createMockAssistantDirector();
        customHook.hook(assistantDirector);

        // Verify that exception was handled
        assertTrue(exceptionHandled.get());
    }

* 📌 Relax Swagger UI version pin. PR [#2089](https://github.com/tiangolo/fastapi/pull/2089) by [@jmriebold](https://github.com/jmriebold).
* 🐛 Fix bug overriding custom HTTPException and RequestValidationError from exception_handlers. PR [#1924](https://github.com/tiangolo/fastapi/pull/1924) by [@uriyyo](https://github.com/uriyyo).