message: python-setup: Fail early if installing for Python 2, and `python2` not available
diff: @@ -5,6 +5,7 @@ import os
  import subprocess
  from tempfile import mkdtemp
  from typing import Optional
  +import shutil
  import extractor_version
  @@ -154,6 +155,17 @@ def install_packages(codeql_base_dir) -> Optional[str]:
  # get_extractor_version returns the Python version the extractor thinks this repo is using
  version = extractor_version.get_extractor_version(codeql_base_dir, quiet=False)
  + if version == 2 and not sys.platform.startswith('win32'):
  + # On Ubuntu 22.04 'python2' is not available by default. We want to give a slightly better
  + # error message than a traceback + `No such file or directory: 'python2'`
  + if shutil.which("python2") is None:
  + sys.exit(
  + "package installation failed: we detected this code as Python 2, but 'python2' executable was not available."
  + "To enable automatic package installation, please install 'python2' before the 'github/codeql-action/init' step, "
  + "such as running 'sudo apt install python2' (Ubuntu 22.04)."
  + "If your code is not Python 2, but actually Python 3, please file a bug report at https://github.com/github/codeql-action/issues/new"
  + )
  +
  if os.path.exists('requirements.txt'):
  print('Found requirements.txt, will install packages with pip', flush=True)
  return install_requirements_txt_packages(version)
  