In summer, httptools upgraded to version 0.3.* as a maintainace release (no functional changes), just changing the packaging and wheel building to support Python 3.10, dropping Python 3.5 support, see here: https://github.com/MagicStack/httptools/releases/tag/v0.3.0

Currently, the uvicorn[standard] dependencies pin httptools at version 0.2.*:

This prevents uvicorn[standard] to use wheels for httptools on Python 3.10 (cp310), often preventing the simple usage of uvicorn[standard] with Python 3.10, as they are only available on httptools>=0.3.0.

Proposed fix:
Either use httptools=0.3.x or drop the pin (initial reason for pinning?)

Explanation
As the httptools upgrade is just a packaging release and Python 3.5 is not supported by uvicorn anyways, upgrading the pinning to 0.3.x (or dropping it entirely, after careful consideration) should not introduce any side-effects or breaking changes for the supported user base, but instead enable the simple usage of Python 3.10 without the need to manually build wheels for httptools on Python 3.10 during pip install

I did not open a pull request yet as I don't know if the pin is intentional and wanted to discuss this first.