Remove promise based debug middleware

[jaw9c]

The exception handling by the debug middleware is broken. If using the toolbar middleware, then any exception raised in a resolver gets consumed and replaced with a cryptic Thread pool related error.

The root cause is that the graphql core lib expects the result of the call to exception instance rather than a rejected promise.

When the graphql core lib tries to resolve the promise as a normal result it results in the cryptic error.

I've also removed the reference to promises as they didn't seem to be helping anything (But please correct the PR if I'm missing something)

[jaw9c]

Potentially fixes #1387

[firaskafri]

Hello @jaw9c, this is great!
Please check the tests as they're failing

[jaw9c]

Thanks @firaskafri - looks like the CI is broken as the tests pass locally.

Just looked at them and appears to be an import error with the examples folder - https://github.com/graphql-python/graphene-django/actions/workflows/tests.yml

[jaw9c]

@firaskafri Updated the PR, tests now get run correctly - was a problem with the python path not being set 👍

[jkimbo]

I'm not that familiar with this part of the codebase but the changes look fine to me.

[firaskafri]

I'm not that familiar with this part of the codebase but the changes look fine to me.

Thank you @jkimbo 🙏