Clean up and test computation of normals in MeshData

[asnt]

Supersedes #2098.

Summary:

• Test computation of face normals.
• Extract computation of face normals and vertex normals out of MeshData for clarity.

[djhoese]

Looks good to me. Let me know if you want to do any more work on this besides what I describe below.

The only thing I'd like is: could you switch your assert statements in the meshdata.py code to if statements with regular ValueError exceptions? It is considered by some linting/complexity/security tools to be bad practice to use assert statements in non-testing code. Let me know what you think.

[asnt]

Looks good to me. Let me know if you want to do any more work on this besides what I describe below.

Thanks @djhoese for the review. That would be all from my side for this PR.

The only thing I'd like is: could you switch your assert statements in the meshdata.py code to if statements with regular ValueError exceptions? It is considered by some linting/complexity/security tools to be bad practice to use assert statements in non-testing code. Let me know what you think.

Agreed. Change applied.

I also changed the relevant raise Exception to raise ValueError.

[djhoese]

Love it! Thank you!