Improved error handling

[randallfrank]

Avoid EnSight / OV hang when running out of disk space. Fixed issues with calculator function docs. Added GLB file generation stub in testing fixtures.

[mariostieriansys]

@randallfrank minor comment Should we move the GLButils class outside of confest.py and just import it? SO the module would still be under tests, it is just to make the code cleaner

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 85.21%. Comparing base (4cece7a) to head (8a43585). Report is 4 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #442 +/- ## ========================================== - Coverage 85.23% 85.21% -0.03% ========================================== Files 19 19 Lines 3488 3489 +1 Branches 443 473 +30 ========================================== Hits 2973 2973 - Misses 430 433 +3 + Partials 85 83 -2 ``` | [Flag](https://app.codecov.io/gh/ansys/pyensight/pull/442/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | Coverage Δ | | |---|---|---| | [](https://app.codecov.io/gh/ansys/pyensight/pull/442/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys) | `85.21% <ø> (-0.03%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ansys#carryforward-flags-in-the-pull-request-comment) to find out more.

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[randallfrank]

@randallfrank minor comment Should we move the GLButils class outside of confest.py and just import it? SO the module would still be under tests, it is just to make the code cleaner

Done!