Rasa-sdk

- [836](https://github.com/rasahq/rasa-sdk/issues/836): Return a json response when encountering action execution exceptions. Log exceptions using logger rather than sanic default print.

- [810](https://github.com/rasahq/rasa-sdk/issues/810): Removed Python 3.6 support.
Updated several dependencies: `sanic`, `httpx`, `websockets`.

No significant changes.

Miscellaneous internal changes
- [592](https://github.com/rasahq/rasa-sdk/issues/592)

- [609](https://github.com/rasahq/rasa-sdk/issues/609)

- [499](https://github.com/rasahq/rasa-sdk/issues/499)

- [441](https://github.com/rasahq/rasa-sdk/issues/441): Slots will be validated in order they are requested. Previously, they were validated in reverse order.

Already extracted slots are now immediately visible during extraction of subsequent slots. Same goes for validation.