Clean up FSLeyes version checking to be less verbose/confusing

[joshuacwnewton]

Checklist

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Description

This PR is meant to simplify the complex error code checking for FSLeyes. Rather than give detailed custom descriptions for every possible case, I've instead opted to echo the native error thrown by the shell.

Our goal with the custom error messages was to try to explain that FSLeyes wasn't present, but that we recommend the tool. That messaging was a bit muddled, though, given that multiple users have interpreted it as a critical error, when instead FSLeyes is optional. So, I was hoping that OPTIONAL DEPENDENCIES would be sufficient for conveying that FSLeyes is a nice to have, but not necessary.

On Ubuntu, it looks like this:

joshua@tadpole:~$ sct_check_dependencies

--
Spinal Cord Toolbox (git-jn/3816-clean-up-fsleyes-dependency-check-dd3bc041faa08e1ae10ab3dcdccd78aa203a674b)

sct_check_dependencies 
--


SYSTEM INFORMATION
------------------
SCT info:
- version: git-jn/3816-clean-up-fsleyes-dependency-check-dd3bc041faa08e1ae10ab3dcdccd78aa203a674b
- path: /home/joshua/repos/spinalcordtoolbox
OS: linux (Linux-5.17.5-76051705-generic-x86_64-with-debian-bookworm-sid)
CPU cores: Available: 4, Used by ITK functions: 4
RAM: Total: 15699MB, Used: 5824MB, Available: 8537MB

MANDATORY DEPENDENCIES
----------------------
Check Python executable.............................[OK]
  Using bundled python 3.7.13 (default, Mar 29 2022, 02:18:16) 
[GCC 7.5.0] at /home/joshua/repos/spinalcordtoolbox/python/envs/venv_sct/bin/python
Check if data are installed.........................[OK]
Check if dipy is installed..........................[OK] (1.5.0)
Check if ivadomed is installed......................[OK] (2.9.6)
Check if matplotlib is installed....................[OK] (3.5.2)
Check if nibabel is installed.......................[OK] (3.2.2)
Check if numpy is installed.........................[OK] (1.21.6)
Check if onnxruntime is installed...................[OK] (1.7.0)
Check if pandas is installed........................[OK] (1.3.5)
Check if portalocker is installed...................[OK] (2.4.0)
Check if psutil is installed........................[OK] (5.9.1)
Check if pyqt5 (5.11.3) is installed................[OK] (5.11.3)
Check if pytest is installed........................[OK] (7.1.2)
Check if pytest-cov is installed....................[OK] (3.0.0)
Check if raven is installed.........................[OK]
Check if requests is installed......................[OK] (2.28.0)
Check if requirements-parser is installed...........[OK]
Check if scipy is installed.........................[OK] (1.7.3)
Check if scikit-image is installed..................[OK] (0.19.3)
Check if scikit-learn is installed..................[OK] (1.0.2)
Check if xlwt is installed..........................[OK] (1.3.0)
Check if tqdm is installed..........................[OK] (4.64.0)
Check if transforms3d is installed..................[OK] (0.3.1)
Check if urllib3 is installed.......................[OK] (1.26.9)
Check if pytest_console_scripts is installed........[OK]
Check if pyyaml is installed........................[OK] (6.0)
Check if wquantiles is installed....................[OK] (0.4)
Check if spinalcordtoolbox is installed.............[OK]
Check ANTs compatibility with OS ...................[OK]
[OK]
Check if figure can be opened with matplotlib.......[OK] (Using GUI backend: 'QtAgg')
Check if figure can be opened with PyQt.............[OK]

OPTIONAL DEPENDENCIES
---------------------
Check FSLeyes version...............................[  ]
   (127, '/bin/sh: 1: fsleyes: not found') 

But, perhaps this is still too intrusive? We could move "Optional Dependencies" to be before "Mandatory Dependencies" so that it isn't the first thing the user sees upon running sct_check_dependencies. That way, it's less likely to spook anyone into thinking that it might be an error, but will still be present for our own debugging (on the forum, etc.)

Very open to discussion here on how it would be best to display this information... 🤔

Linked issues

Fixes #3816.

[codecov]

Codecov Report

Merging #3820 (a5e1e24) into master (9c6441c) will increase coverage by 0.00%.
The diff coverage is 0.00%.

Flag	Coverage Δ
api-tests	21.87% <0.00%> (+<0.01%)	⬆️
cli-tests	58.77% <0.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...pinalcordtoolbox/scripts/sct_check_dependencies.py	0.00% <0.00%> (ø)

[mguaypaq]

The output is as discussed in the SCT dev meeting, so LGTM. Thanks!