Feature: Add $MDSPLUS_DIR/python to PYTHONPATH in etc/envsyms

[WhoBrokeTheBuild]

This removes the long-broken MDSPLUS_SETUP_PY and instead adds $MDSPLUS_DIR/python to the PYTHONPATH in $MDSPLUS_DIR/etc/envsyms.
This should allow users to import MDSplus in python after an install with no additional setup

Also add import MDSplus steps to the installer tests

[mwinkel-dev]

Simple change. Looks good. Approving this because I'm assuming Jenkins will rebuild it.

Note though that one of the "Test Packages" tests failed because it returned exit status 42.

[dgarnier]

I agree this is consistent with the current use of PYTHONPATH and MDSplus. However, I'm not a huge fan of this whole mechanism and at OpenStar we are doing something entirely different and explicitly not relying on PYTHONPATH.. preferring to use venv based solutions (see my request to have MDSplus build its own wheel during the install instead).

This change would effectively just have me modify our environment to take it back out... so I'm not a fan of this change.

[WhoBrokeTheBuild]

For what it's worth Darren I agree, there's a reason I haven't implemented this in all the years we've been fighting with the python package install. You can see the discussions in the discord that lead to this PR being submitted.

I'm also not a fan of the wheel solution because it (as I understand it) places a copy of the python files in the venv rather than pointing to the $MDSPLUS_DIR/python folder, which makes sense for most packages but I don't like it for ours.

Then there's the additional issues of trying to modify the default python environment on install, and while users can absolutely setup a venv I would really like import MDSplus to work on a fresh install.

With some effort, I could probably get MDSPLUS_SETUP_PY to trigger adding PYTHONPATH=$MDSPLUS_DIR/python to etc/envsyms if people would refer that? It means that this will only affect the users that want it, which is good, but then it also won't affect users who don't know about the rather obscure variable.

[dgarnier]

I'm also not a fan of the wheel solution because it (as I understand it) places a copy of the python files in the venv rather than pointing to the $MDSPLUS_DIR/python folder, which makes sense for most packages but I don't like it for ours.

Oh. That gives me an idea. Let me see if it works. I think a wheel can be made that does just what you want.. just installs a .pth that points to $MDSPLUS_DIR/python (or the absolute install directory which is probably actually what we want. I'll send a PR if it works.