maintenance tasks

[belm0]

The purerpc repo was transferred to python-trio. Here are the short-term tasks I'm intending, with the goal of pushing a maintenance release to pypi for active dependees that may be having problems with the old anyio 1.x dependency of this package:

• [x] note on README crediting original author, explain that the project is in maintenance mode (keep things working for active dependees), point to https://github.com/grpc/grpc for people needing asyncio only
• [x] misc: doc updates, TODO's I noted while walking through the code, prune unused imports
• [x] set up CI (travis-ci.org is defunct, use github actions), pin requirements for reproducible tests
• [x] upgrade to anyio 3.x. It does imply that curio support will be dropped. Related to the upgrade, Server.serve() will be strongly discouraged in favor of a newly-added Server.serve_async(). PR #33
• [x] drop Python 3.5 and 3.6 support - they are past end of life, and it's a large burden to the implementation verbosity and performance (async_generator shim, etc.)
• [x] remove runtime patching of anyio.run(). This was to support backend="uvloop" (run() already supports use_uvloop backend-specific option, use the correct way) and the PURERPC_BACKEND environment variable (introduce something like purerpc_run()).
• [x] tag release and push to pypi

[standy66]

I also seem to have used private APIs like anyio._networking and anyio._get_async_lib() back then to get around some issues. I guess we should get rid of this to maintain better compatibility across anyio versions.

Also, maybe there is a way we can get rid of hyper-h2 monkey patches?

[belm0]

additionally: drop Python 3.5 and 3.6 support, since they are past end of life, and it's a large burden to the implementation verbosity and performance (async_generator shim, etc.)

[belm0]

released v0.7.0