Eagerly validate using a compatible OS

[Eric-Arellano]

In the past month, we've had two users confused from trying to use macOS 10.14. The error message is quite cryptic:

$ ./pants test algorithms::
Bootstrapping Pants using /Users/user/.pyenv/shims/python3.9
Installing pantsbuild.pants==2.5.0 into a virtual environment at /Users/user/.cache/pants/setup/bootstrap-Darwin-x86_64/2.5.0_py39
created virtual environment CPython3.9.2.final.0-64 in 353ms
  creator CPython3Posix(dest=/Users/user/.cache/pants/setup/bootstrap-Darwin-x86_64/pants.xGjbPP/install, clear=False, no_vcs_ignore=False, global=False)
  seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/Users/sohum/Library/Application Support/virtualenv)
    added seed packages: pip==21.1.2, setuptools==57.0.0, wheel==0.36.2
  activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
Requirement already satisfied: pip in /Users/user/.cache/pants/setup/bootstrap-Darwin-x86_64/pants.xGjbPP/install/lib/python3.9/site-packages (21.1.2)
Collecting pip
  Using cached pip-21.2.4-py3-none-any.whl (1.6 MB)
Installing collected packages: pip
  Attempting uninstall: pip
    Found existing installation: pip 21.1.2
    Uninstalling pip-21.1.2:
      Successfully uninstalled pip-21.1.2
Successfully installed pip-21.2.4
ERROR: Could not find a version that satisfies the requirement pantsbuild.pants==2.5.0 (from versions: 0.0.17, 0.0.18, 0.0.20, 0.0.21, 0.0.22, 0.0.23, 0.0.24, 0.0.25, 0.0.26, 0.0.27, 0.0.28, 0.0.29, 0.0.30, 0.0.31, 0.0.32, 0.0.33, 0.0.34, 0.0.35, 0.0.36, 0.0.37, 0.0.38, 0.0.39, 0.0.40, 0.0.41, 0.0.42, 0.0.43, 0.0.44, 0.0.45, 0.0.46, 0.0.47, 0.0.48, 0.0.49, 0.0.50, 0.0.51, 0.0.52, 0.0.53, 0.0.54, 0.0.55, 0.0.56, 0.0.57, 0.0.58, 0.0.59, 0.0.60, 0.0.61, 0.0.62, 0.0.63, 0.0.64, 0.0.65, 0.0.66, 0.0.67, 0.0.68, 0.0.69, 0.0.70, 0.0.71, 0.0.72, 0.0.73, 0.0.74, 0.0.75, 0.0.76, 0.0.77, 0.0.79, 0.0.80, 0.0.81, 0.0.82, 1.0.0, 1.0.1, 1.1.0, 1.2.0, 1.2.1, 1.3.0, 1.4.0, 1.5.0, 1.6.0, 1.7.0, 1.15.0, 1.16.0, 1.17.0, 1.18.0, 1.19.0, 1.20.0, 1.21.0, 1.22.0, 1.23.0, 1.24.0, 1.25.0, 1.26.0, 1.27.0, 1.28.0)
ERROR: No matching distribution found for pantsbuild.pants==2.5.0

Instead, we can eagerly detect if using an invalid OS and print a nice error message with your options.