Motivation for this change

New version available which adds support for the ESP32.
Now, the tests using flake8 are also enabled.
I even tested the upload of some binaries to a real-world ESP8266.

If you want, I can also refactor the derivation to use fetchPypi and call it in python-packages.nix instead of all-packages.nix. Just let me know if that's desired.

@dezgeg

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • Linux
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.