Updates for python3 "native"

Make changes to support distributions where Python is provided as python3 (such as Ubuntu 22.04).

Change explicit mention of Python binary to python3 which should be supported by all distributions and environments (https://peps.python.org/pep-0394/).

Update hash bangs to python3.

Adapt CMake to search for pytest also as pytest-3; likewise for nosetest binary as nosetests3 (with fallback to pytest and nosetests, which can be used in some virtual environments, even with a Python 3 install).

Remove unnecessary utf-8 encoding lines.

Update test scripts to python3

I did have one uncertainty about the current PR, which is that in the testGaudiToolbox.cmake file the PYTHONPATH is set to the Gaudi sources directory, because the dummy project Python in the build doesn't have the right Python module files:

➜  Gaudi ls dummyProjectBinaryDir/python/dummyProject
__init__.py  __pycache__

Is this expected? Or should the dummyModule.py and dummy.py files have been copied to the build area.

It wasn't very clear to me.

assigned to @clemenci

added lhcb-gaudi-head label

changed milestone to %v36r10

• [2023-01-27 00:03] Validation started with lhcb-gaudi-head#3457
• [2023-01-27 00:13] Validation started with lhcb-run2-gaudi-head#446
• [2023-01-28 00:03] Validation started with lhcb-gaudi-head#3458
• [2023-01-28 00:21] Validation started with lhcb-run2-gaudi-head#447
• [2023-01-29 00:03] Validation started with lhcb-gaudi-head#3459
• [2023-01-29 00:21] Validation started with lhcb-run2-gaudi-head#448
• [2023-01-30 10:13] Validation started with lhcb-gaudi-head#3460
• [2023-01-31 00:04] Validation started with lhcb-gaudi-head#3461
• [2023-01-31 00:12] Validation started with lhcb-run2-gaudi-head#449
• [2023-02-01 00:05] Validation started with lhcb-gaudi-head#3462
• [2023-02-01 07:27] Validation started with lhcb-gaudi-head#3463
• [2023-02-01 07:45] Validation started with lhcb-run2-gaudi-head#450
• [2023-02-02 00:05] Validation started with lhcb-gaudi-head#3464
• [2023-02-03 00:05] Validation started with lhcb-gaudi-head#3465
• [2023-02-03 00:14] Validation started with lhcb-run2-gaudi-head#451

approved this merge request

resolved all threads

mentioned in issue #256

merged

mentioned in commit bf64acfa