* **exception_handlers** - A mapping of either integer status codes,
or exception class types onto callables which handle the exceptions.
Exception handler callables should be of the form
- `handler(request, exc) -> response` and may be be either standard functions, or
+ `handler(request, exc) -> response` and may be either standard functions, or
async functions.
* **on_startup** - A list of callables to run on application startup.
Startup handler callables do not take any arguments, and may be be either