Tools: stop requiring python-is-python3 package

[peterbarker]

No description provided.

[Ryanf55]

If you uninstall this, you find that waf can't run.

$ ./Tools/autotest/sim_vehicle.py -v ArduPlane -DG --console --enable-dds
SIM_VEHICLE: Start
SIM_VEHICLE: Killing tasks
SIM_VEHICLE: Starting up at SITL location
SIM_VEHICLE: WAF build
SIM_VEHICLE: Configure waf
SIM_VEHICLE: "/home/ryan.friedman/Dev/ardu_ws/src/ardupilot/modules/waf/waf-light" "configure" "--board" "sitl" "--debug" "--enable-dds"
/usr/bin/env: ‘python’: No such file or directory
SIM_VEHICLE: (Configure waf) exited with code 32512
SIM_VEHICLE: Killing tasks

It was the python team's recommendation to update shebangs if a script could run on python3, to say python3.
This shouldn't be a huge change, and you can run python3 on Ubuntu 18 (bionic) which is EOL. On Ubuntu 20 (focal), python3 is the default.

docker run --net host -it ubuntu:18.04 bash
#apt update
#apt install python-dev
# which python
/usr/bin/python
# python --version
Python 2.7.17
# apt install python3-dev
# python3 --version
Python 3.6.9

To me, the risk of impacting people is low because we already install python3-dev in ubuntu 18.

ardupilot/Tools/environment_install/install-prereqs-ubuntu.sh

Lines 85 to 89 in 33d75f1

	if [ ${RELEASE_CODENAME} == 'bionic' ] ; then
	SITLFML_VERSION="2.4"
	SITLCFML_VERSION="2.4"
	PYTHON_V="python3"
	PIP=pip3

[khancyr]

We don't support py2 anymore (or not actively), so yes let's go into this direction !

[Ryanf55]

When we do this, we can also remove the # encoding: utf-8 line, that's only needed in python2 scripts.

[peterbarker]

OK, all good, full-steam ahead.

[Ryanf55]

First action seems to go request to the waf maintainer if they would be interested in following these recommendations: https://peps.python.org/pep-0394/#for-python-script-publishers

[peterbarker]

First action seems to go request to the waf maintainer if they would be interested in following these recommendations: https://peps.python.org/pep-0394/#for-python-script-publishers

What entry-point are you worried about? waf-light? I usually use ./waf so I wouldn't get the problem :-)

Have you checked to see if it has been updated upstream?

We could probably also carry a trivial patch for it if required.

[Ryanf55]

First action seems to go request to the waf maintainer if they would be interested in following these recommendations: https://peps.python.org/pep-0394/#for-python-script-publishers

What entry-point are you worried about? waf-light? I usually use ./waf so I wouldn't get the problem :-)

I removed python-is-python3 and it errored out in the waf submodule when building, so that's why I thought to start there.

Have you checked to see if it has been updated upstream?

Yea, I checked upstream, it's still using /usr/bin/env python and there's nothing on the issue tracker about it.

We could probably also carry a trivial patch for it if required.

For sure! It should be easy to whip up. I'll give it a go unless you're bored.

[peterbarker]

We could probably also carry a trivial patch for it if required.

For sure! It should be easy to whip up. I'll give it a go unless you're bored.

Please go ahead. See what happens if you PR upstream too?

[peterbarker]

@Ryanf55 I've created a trivial PR against our waf fork to use python3 and referenced it in here.

I think past this we don't require python to be in your path.

I've left the environment install stuff alone, on the basis that without it you can't check out 4.5 and expect things to work without more hackery. Maybe in 4.7 we can get rid of those.