SCons: Bump min version to 3.1.2, test it on CI with one Linux job

[akien-mga]

The min SCons version had to be bumped as SCons 3.0 before 3.0.3 seems broken (see below), and there's little gain from supporting 3.0.3-3.0.5.

3.1.2 is also the first version to avoid ambiguities between Python 2 and Python 3 usage, so we finally use it as the minimum baseline.

Also test against Python 3.6 which is also our minimum supported version.
This should help prevent regressions whenever we modernize the build scripts.

Also a bunch of cosmetic changes, got carried away :P

This should fail initially because of #91986, so I will rebase after #92041 is merged.
Confirmed, so #92041 is now included in this PR.

CC @Repiteo @AThousandShips

[akien-mga]

Had to install wheel before scons, otherwise it failed with this error:

3.6.15 (default, Sep  6 2021, 07:07:23) 
[GCC 9.3.0]
Collecting scons==3.0.0
  Downloading scons-3.0.0.tar.gz (630 kB)
  Preparing metadata (setup.py): started
  Preparing metadata (setup.py): finished with status 'done'
Using legacy 'setup.py install' for scons, since package 'wheel' is not installed.
Installing collected packages: scons
    Running setup.py install for scons: started
    Running setup.py install for scons: finished with status 'error'
    ERROR: Command errored out with exit status 1:
     command: /opt/hostedtoolcache/Python/3.6.15/x64/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-c84v8i3g/scons_e21b17358cca4fa0a6913eec3e36b727/setup.py'"'"'; __file__='"'"'/tmp/pip-install-c84v8i3g/scons_e21b17358cca4fa0a6913eec3e36b727/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-9y39lo61/install-record.txt --single-version-externally-managed --compile --install-headers /opt/hostedtoolcache/Python/3.6.15/x64/include/python3.6m/scons
         cwd: /tmp/pip-install-c84v8i3g/scons_e21b17358cca4fa0a6913eec3e36b727/
    Complete output (6 lines):
    usage: setup.py [global_opts] cmd1 [cmd1_opts] [cmd2 [cmd2_opts] ...]
       or: setup.py --help [cmd1 cmd2 ...]
       or: setup.py --help-commands
       or: setup.py cmd --help
    
    error: option --single-version-externally-managed not recognized
    ----------------------------------------
ERROR: Command errored out with exit status 1: /opt/hostedtoolcache/Python/3.6.15/x64/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-c84v8i3g/scons_e21b17358cca4fa0a6913eec3e36b727/setup.py'"'"'; __file__='"'"'/tmp/pip-install-c84v8i3g/scons_e21b17358cca4fa0a6913eec3e36b727/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-9y39lo61/install-record.txt --single-version-externally-managed --compile --install-headers /opt/hostedtoolcache/Python/3.6.15/x64/include/python3.6m/scons Check the logs for full command output.

[akien-mga]

Confirmed that the build fails as expected without #92041: https://github.com/godotengine/godot/actions/runs/9124804393/job/25089728389?pr=92043

Building with flags: platform=linuxbsd target=editor tests=true verbose=yes warnings=extra werror=yes module_text_server_fb_enabled=yes dev_build=yes use_asan=yes use_ubsan=yes use_llvm=yes linker=lld
scons: Reading SConscript files ...
TypeError: 'SConsEnvironment' object is not a mapping:
  File "/home/runner/work/godot/godot/SConstruct", line 368:
    opts.Update(env, {**ARGUMENTS, **env})

I'll rebase to include that PR.

[AThousandShips]

Looks great and very helpful, approving on principle but needs to pass compilation, something with the configuration fixes if the environment I suspect

Could be specific to 3.0.0, might be worth trying with 3.1.2 which has some changes, like python dependencies, unsure

[akien-mga]

Indeed, that's a weird error:

Checking for C header file mntent.h... TypeError : sequence item 0: expected str instance, bytes found

https://github.com/godotengine/godot/actions/runs/9124860447/job/25089907695?pr=92043

I can't reproduce it locally with a python:3.6 environment in podman, so not sure how to debug.
Assuming the error does happen on the SCons CheckHeader method, it's not something we can patch ourselves.

I'll throw a few tests on GitHub actions in my fork to see if newer Python or SCons solves it.

• SCons 3.0.0, Python 3.7: Broken. https://github.com/akien-mga/godot/actions/runs/9125224114/job/25091025641
• SCons 3.1.0, Python 3.6: Works. https://github.com/akien-mga/godot/actions/runs/9125233038/job/25091041456
• SCons 3.0.5, Python 3.6: Works. https://github.com/akien-mga/godot/actions/runs/9125414437/job/25091590049
• SCons 3.0.3, Python 3.6: Works. https://github.com/akien-mga/godot/actions/runs/9125447833/job/25091688068
• SCons 3.0.2, Python 3.6: Doesn't exist in pip repo. https://github.com/akien-mga/godot/actions/runs/9125491629/job/25091824674
• SCons 3.0.1, Python 3.6: Broken. https://github.com/akien-mga/godot/actions/runs/9125347389/job/25091404140

So in short, we could makek SCons 3.0.3 the min supported version to work around this bug.

Based on https://repology.org/project/scons/versions, that would exclude Debian 10 and derivatives which have SCons 3.0.1, but I think it's fine by now. Debian 10 will be EOL in a month: https://wiki.debian.org/LTS

We don't gain much from supporting 3.0.3-3.0.5 though, hardly any distro provides it.
Quite a few distros have 3.1.2, some have 3.1.1, none seems to have 3.1.0 but if it works, I think we can use it as the baseline.

[AThousandShips]

I think it'd be worth raising the minimum version, unless that excludes a large number of environments, like automated tools somewhere, but otherwise I'd say it isn't worth the hassle to plug holes and provide workarounds

I think large distros like LTS Ubuntu etc. are a good reference especially when automatic configuration etc. is involved like CI and containers

[akien-mga]

I bumped the minimum SCons version to 3.1.0 as described above.

[AThousandShips]

Could be worth considering bumping to 3.1.2 given the note in the build instructions (they will also need updating, with 3.1.0 at least):

If your distribution uses Python 2 by default, or you are using a version of SCons prior to 3.1.2, you will need to change the version of Python that SCons uses by changing the shebang (the first line) of the SCons script file to #! /usr/bin/python3. Use the command which scons to find the location of the SCons script file.

[akien-mga]

Bumped to 3.1.2 in the end.
Next stop, 4.0.0, sometime next year maybe?

[AThousandShips]

That sounds reasonable I think, it'll be 5 years old by then and I think we can treat that as a reasonable backwards range