Require httpx 0.13

[hugovk]

This PR is really an issue in the form of a PR to demonstrate RESPX does not yet support the new httpx 0.13 release.

The internal concurrency _backends was dropped from httpx in encode/httpx#901.

Example tests failure:

• https://github.com/hugovk/respx/runs/702618287?check_suite_focus=true

httpx 0.13 is intended to be the last before the 1.0 release:

• https://twitter.com/_tomchristie/status/1263789740337364992

[florimondmanca]

It might be quite interesting to see if RESPX can now leverage the newly public Transport API to provide a complete « here’s how to send a mocked request » backend instead of patching the networking calls...

But that would probably require users to pass a transport=... parameter to their client - which is typically not possible assuming the requests being mocked are made in a different part of the code.

But then maybe the proposed mount API https://github.com/encode/httpx/issues/977 could be useful to « patch » the default transports for http:// and https://... Not sure at this point.

In any case, the concurrency backends aren’t gone. They were moved to the httpcore package since the networking layer is now handled there. So as a hot fix it should be possible to import them from there instead of HTTPX.

[lundberg]

Yes @florimondmanca this will be interesting and fun to solve 😅, multiple paths and choices to tackle.

[lundberg]

Closing this in favour of #57 .

@florimondmanca RESPX mocking is now handled as a transport 🎉

[lundberg]

@hugovk please try out #57