fix Signal issue with Sanic 21.9

[wochinge]

Proposed Changes

• fix Problem with sanic>21.6 #61

[wochinge]

Should I also update poetry.lock? We might also wanna double check if this actually works with older Sanic versions

[indam23]

I've ported this fix to #66 and added the changes mentioned in the issue

[wochinge]

@ancalita @melindaloubser1 there is also an official test library for Sanic (https://sanic.dev/en/plugins/sanic-testing/getting-started.html) which I’d recommend to use instead of pytest-sanic. I switched out the Rasa X code with that one and it was relatively straight forward if I remember correctly

[indam23]

Thanks for the tip @wochinge 🙏

[ottonemo]

@yunstanford do you think this can be merged? This prevents people from using current sanic versions :)