tests/test-check-py3-commands.t

posix: simplify checkexec check

Use a slightly simpler logic that in some cases can avoid an unnecessary chmod
and stat.

Instead of flipping the X bits, make it more clear that we rely on no X bits
being set on initial file creation, and that at least some of them stick after
they all have been set.

#require py3exe

This test helps in keeping a track on which commands we can run on
Python 3 and see what kind of errors are coming up.
The full traceback is hidden to have a stable output.

  $ for cmd in version debuginstall ; do
  >   echo $cmd
  >   $PYTHON3 `which hg` $cmd 2>&1 2>&1 | tail -1
  > done
  version
  NameError: name 'basestring' is not defined
  debuginstall
  NameError: name 'basestring' is not defined