Running bummr with an invalid flag shows deprecation warning

If I type:
`bummr --foobar`
The output I get is
```
Could not find command "__foobar".
Deprecation warning: Thor exit with status 0 on errors. To keep this behavior, you must define `exit_on_failure?` in `Bummr::CLI`
You can silence deprecations warning by setting the environment variable THOR_SILENCE_DEPRECATION.
```