Thank you!

For PyPy3/Linux: do we need to update MB_ML_VER to 2014 and DOCKER_TEST_IMAGE to focal in build.sh?

if [[ "$MB_PYTHON_VERSION" == pypy3* ]]; then
  if [[ "$TRAVIS_OS_NAME" != "macos-latest" ]]; then
    MB_ML_VER="2010"
    DOCKER_TEST_IMAGE="multibuild/xenial_$PLAT"
  else
    MB_PYTHON_OSX_VER="10.9"
  fi
fi

And this is likely a longer term multibuild question and not immediately relevant here: should it use something newer than Trusty 14.04?

https://github.com/pypa/manylinux

manylinux2010 (CentOS 6 based - EOL)

Since 2010 is EOL, updating to MB_ML_VER to 2014 seems like a good idea, sure.

As has been said, there aren't focal docker images for 32-bit. Is dropping support for 32-bit Linux wheels something that we're interested in doing? At the very least, I didn't think that this PR was the right place for that.

Regarding other options, there are some problems at the moment -

• For 64-bit, if I try updating DOCKER_TEST_IMAGE to focal for Linux PyPy, ...something isn't right. PLAT isn't being passed in for some reason - https://github.com/radarhere/pillow-wheels/runs/3430741826

/usr/bin/choose_python.sh: line 68: python: command not found

(edit: added in #218)

• If I try xenial instead, there's another problem - https://github.com/radarhere/pillow-wheels/runs/3432713147?check_suite_focus=true#step:4:6972

Features should be: 'fribidi harfbuzz raqm transp_webp webp_anim webp_mux xcb'; but are 'transp_webp webp_anim webp_mux xcb'

• xenial is also not working for Python 3.10 currently - https://github.com/radarhere/pillow-wheels/runs/3432713284#step:4:6600 (edit: it seems there isn't interest in supporting Python 3.10 in the images, Update pip to 21.2.3 for Python 3.10 multi-build/docker-images#12 (comment))

AttributeError: module 'sysconfig' has no attribute 'get_preferred_scheme'

So this PR is the simplest option for the moment.

The point of this PR is to add 3.10 for Linux, so agreed best to keep it simple and let's merge this. Thanks for trying that lot out.

Dropping 32-bit: something to consider, download numbers are pretty low, but let's discuss it another time in the main repo.

Thanks again!