Use logging/warnings instead of print when loading force constants from Phonopy

[RastislavTuranyi]

Hi!

Loading force constants from Phonopy can generate multiple "warnings" e.g. Force constants not found in 4-benzylaniline_683106-phonopy.yaml, attempting to read from 4-benzylaniline_683106-force_constants.hdf5 which takes a lot of terminal space when I run many calculations in a script. Therefore, I tried looking into disabling these stdout prints, but it turned out that they are hardcoded print statements.

Would it be possible to use something like logging or warnings.warn to log these messages? That way, it would be possible to intercept them upstream

[ajjackson]

This would technically be a breaking change, but it would indeed be nice to have the verbosity control that logging provides. (And allow us to print more debug information!)

Have you considered using https://docs.python.org/3/library/contextlib.html#contextlib.redirect_stdout in the script?

To discard standard output from a function:

with redirect_stdout(None):
    run_something()

Or to store it to a list:

buffer = io.StringIO()
with redirect_stdout(buffer):
    run_something()
    
buffer.seek(0)
lines = buffer.readlines()

[ajjackson]

Perhaps we should create a wider Issue to consider using logging consistently across Euphonic for versions 2.x

[ajjackson]

Closing as wontfix because we won't treat Phonopy reader specially. Opening separate issue for wider discussion of logging.