Better shell specific testing

[davidlatwe]

• fix rez-env output test is not testing on specified shell #1135,

• also, able to exclude specific shells from testing with @per_available_shell(). This is currently as a helper feature for working on test_rez_env_output.

  Example usage as follow:

      @per_available_shell(exclude=["cmd", "powershell"])
      @install_dependent()
      def test_rez_env_output(self):
          ...

[davidlatwe]

I didn't use process.returncode is because, it seems that powershell always return 0 even the command actually failed.

[bfloch]

Isn't this a case of powershell -File vs. -Command?
Only the latter passes the error code.
https://stackoverflow.com/questions/50200325/returning-an-exit-code-from-a-powershell-script

Or maybe $ErrorActionPreference = "Stop":
https://stackoverflow.com/questions/9948517/how-to-stop-a-powershell-script-on-the-first-error

The checks also need to happen form $LastExitCode I believe:
https://stackoverflow.com/questions/10666035/difference-between-and-lastexitcode-in-powershell

What an over-engineered little shell :)

[davidlatwe]

Hmmm, looks like checking stderr isn't a good idea ? test_rez_env_output failed on csh shell :(

Edit
Ah, that should be because the csh isn't the default shell on Ubuntu and Mac, as powershell isn't the defaule shell on Windows, they all got flushed out after rez-env --shell flag is used !

txt = '!hey>$'

    def _test(txt):
        # Assumes that the shell has an echo command, build-in or alias
        binpath = os.path.join(system.rez_bin_path, "rez-env")
        args = [binpath, "--shell", target_shell, "--", "echo", txt]
    
        process = subprocess.Popen(
            args, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
            stderr=subprocess.PIPE, universal_newlines=True
        )
        sh_out = process.communicate()
        if sh_out[1]:
>           raise Exception("Command failed:\n%s" % sh_out[1])
E           Exception: Command failed:
E           hey: Event not found.
E            (in shell 'csh')

[davidlatwe]

Github action cannot find any runner that matches ubuntu-16.04, due to :
https://github.blog/changelog/2021-04-29-github-actions-ubuntu-16-04-lts-virtual-environment-will-be-removed-on-september-20-2021/

Ubuntu version bumped in test matrix.