Add httpx tracing extension

[inirudebwoy]

Hi 😄
I have been missing httpx https://www.python-httpx.org package extension so I create one.
Thankfully httpx is very similar to requests so most of my code is actually taken from requests extension.
If this is a problem I can address it somehow 😄

[macieyng]

@lzchen can we get your help with that PR? Our project and other people could benefit greatly from it 🙏

[TobKed]

inirudebwoy try rebase on the latest master. Maybe it will help fix CI.

[TobKed]

PTAL @lzchen @aabmass @hectorhdzg @jeremydvoss

[lzchen]

@inirudebwoy
Could you add a README.rst file? Please make sure to include an example of how to use this in code.

[lzchen]

@inirudebwoy
Thanks for the contribution and apologies for the long delay before the review. The changes look good to me. I've left a few comments. Could you also rebase to the latest master commit, fix the failing builds and update some of the version dependencies

[inirudebwoy]

@lzchen Applied your recommendations. Tests are passing. Is there anything else you think needs to be changed?

[lzchen]

@inirudebwoy

Looks good. Thanks for the contribution. Looks like builds are still failing for py27 and p35. Are those versions supported for httpx?

[inirudebwoy]

@lzchen No they are not. httpx supports Python 3.7+. I have updated setup.py and (hopefully) tox.ini.

[lzchen]

Our unit test builds for python versioning is a bit complex right now due to some packages not supporting the older python versions. For now you can modify the commands in tox.ini like this:

py3{7,8,9}-unit: {[constants]unit-base-command}
py36-unit: {[constants]unit-base-command} --ignore=contrib/opencensus-ext-httpx
py{27,34,35}-unit: {[constants]unit-base-command} --ignore=contrib/opencensus-ext-stackdriver --ignore=contrib/opencensus-ext-flask --ignore=contrib/opencensus-ext-httpx

That should make the builds pass.

[inirudebwoy]

@lzchen thanks. Done that now.

[miqm]

@lzchen do you have any ETA when you will publish this extension?