bugfix: fix check for normalized quaternion

[javierggt]

Description

I discovered that the Quaternion can be initialized with an invalid q.

In some places the class assumes that quaternions are normalized, and it tries to enforce that in the q property. However, the check is not correct, and instead it checks that the norm is less than 1. For example, the following does not raise:

from Quaternion import Quat
q = Quat([0, 0, 0, 0.1])

This PR fixes this and adds the corresponding test to catch the issue.

Also, there was one test that was using q=[0, 0, 0, 0], which is useless in all our use cases and can't be normalized. Using q=[0, 0, 0, 0] will raise an exception from now on and the test was fixed.

Interface impacts

A bug was fixed in the constructor that allowed non-normalized quaternions. In particular, it allowed Quat(q=[0, 0, 0, 0]), which might be used (incorrectly) in some places. From now on this will raise an exception.

Testing

Unit tests

• No unit tests
• Mac on version 4.3.1.dev4+g2db69e2
• Linux
• Windows

(ska3-flight) javierg Quaternion $ pytest Quaternion/
========================================= test session starts =========================================
platform darwin -- Python 3.10.8, pytest-7.2.1, pluggy-1.0.0
rootdir: /Users/javierg/SAO/git, configfile: pytest.ini
plugins: timeout-2.1.0, anyio-3.6.2
collected 72 items                                                                                    

Quaternion/tests/test_all.py ..............................................                     [ 63%]
Quaternion/tests/test_shaped.py ..........................                                      [100%]

========================================= 72 passed in 3.83s ==========================================
(ska3-flight) javierg Quaternion $ python -c "import Quaternion; print(Quaternion.__version__)"
4.3.1.dev4+g2db69e2

Independent check of unit tests by [REVIEWER NAME]

• [PLATFORM]:

Functional tests

No functional testing.

[taldcroft]

Looks good code-wise. Just update the description to reflect the final PR and add the output of your pytest run and git rev-parse HEAD.

[javierggt]

@taldcroft Done

[taldcroft]

LGTM