diff tests/hghave @ 45849:c102b704edb5

global: use python3 in shebangs

Python 3 is the future. We want Python scripts to be using Python 3
by default.

This change updates all `#!/usr/bin/env python` shebangs to use
`python3`.

Does this mean all scripts use or require Python 3: no.

In the test environment, the `PATH` environment variable in tests is
updated to guarantee that the Python executable used to run
run-tests.py is used. Since test scripts all now use
`#!/usr/bin/env python3`, we had to update this code to install
a `python3` symlink instead of `python`.

It is possible there are some random scripts now executed with the
incorrect Python interpreter in some contexts. However, I would argue
that this was a pre-existing bug: we should almost always be executing
new Python processes using the `sys.executable` from the originating
Python script, as `python` or `python3` won't guarantee we'll use the
same interpreter.

Differential Revision: https://phab.mercurial-scm.org/D9273

--- a/tests/hghave	Mon Nov 09 09:58:44 2020 -0800
+++ b/tests/hghave	Fri Nov 06 13:58:59 2020 -0800
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Test the running system for features availability. Exit with zero
 if all features are there, non-zero otherwise. If a feature name is
 prefixed with "no-", the absence of feature is tested.