Nexus: Allow bandstructure plotting with custom k-path

[mcbennet]

Proposed changes

This PR adds to the function plot_bandstructure in ./nexus/lib/pwscf_analyzer.py. It allows the user to provide a custom set of labels for the high symmetry k-points (in the form k_labels=['GAMMA','','','','M','','',...]) where the length of the label array should match the number of k-points in the analyzer object. When custom labels are give, spglib is no longer used since it is assume that the k-points in the analyzer object are different from the ones that would be generated by spglib.

What type(s) of changes does this code introduce?

• New feature

Does this introduce a breaking change?

• No

What systems has this change been tested on?

Laptop. Linux

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• N/A. Code added or changed in the PR has been clang-formatted
• No. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• No. Documentation has been added (if appropriate)

[qmc-robot]

Can one of the admins verify this patch?

[prckent]

We should probably add this to the PR template: are any python package dependencies changed?

[mcbennet]

We should probably add this to the PR template: are any python package dependencies changed?

None of the dependencies are altered.

[ye-luo]

Test this please