Prepare to move to Python 3.9 venv, build fails ciso8601

So I am preparing to move HA to Python 3.9, setting up a new venv to build everything in.
I’m running Ubuntu Focal, 20.04.

This has never been an issue before but now I’m failing on creating wheel for ciso8601, complete error code:

Building wheels for collected packages: ciso8601
  Building wheel for ciso8601 (pyproject.toml) ... error
  ERROR: Command errored out with exit status 1:
   command: /srv/homeassistant/bin/python3 /srv/homeassistant/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/ build_wheel /tmp/tmp39k1t1uf
       cwd: /tmp/pip-install-kb1ribjl/ciso8601_05bed17d32934649aecf1ba629960f71
  Complete output (17 lines):
  running bdist_wheel
  running build
  running build_py
  package init file 'ciso8601/' not found (or not a regular file)
  creating build
  creating build/lib.linux-x86_64-3.9
  creating build/lib.linux-x86_64-3.9/ciso8601
  copying ciso8601/__init__.pyi -> build/lib.linux-x86_64-3.9/ciso8601
  copying ciso8601/py.typed -> build/lib.linux-x86_64-3.9/ciso8601
  running build_ext
  creating build/temp.linux-x86_64-3.9
  x86_64-linux-gnu-gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -g -fwrapv -O2 -fPIC -DCISO8601_VERSION=2.2.0 -DCISO8601_CACHING_ENABLED=1 -I/srv/homeassistant/include -I/usr/include/python3.9 -c module.c -o build/temp.linux-x86_64-3.9/module.o
  module.c:1:10: fatal error: Python.h: No such file or directory
      1 | #include <Python.h>
        |          ^~~~~~~~~~
  compilation terminated.
  error: command '/usr/bin/x86_64-linux-gnu-gcc' failed with exit code 1
  ERROR: Failed building wheel for ciso8601
Failed to build ciso8601
ERROR: Could not build wheels for ciso8601, which is required to install pyproject.toml-based projects

I’m not sure what I can do as it seems to be a problem with the build/init files?

During this process i f*cked up my 3.8 venv aswell so I’m having issues with my production build aswell, not superbreaking but some components wont run and I cannot check config and restart HA from “Server controls”. But thats something for another thread.

Any pointers to my main 3.9 issue?


Jesus christ. This so basic I’m mad.


(missing dev packages)

I too stumbled upon the same issue. In my case this solved the issue -

apt install python3.9

apt install python3.9-dev

apt install python3.9-venv

sudo pip3 install ciso8601 --no-binary :all:

make sure you have install build essential

sudo apt install build-essential