Method for locating MAS data files is not robust

[cooperdowns]

The current glob syntax for locating MAS data files of a specific variable (e.g. t001.hdf t002.hdf, etc.) will match with unwanted stuff, such as a random file called test.txt or tmas and then the call to read the variable (e.g. t = mas_output['t']) will crash ungracefully complaining about coordinates.

Also, if there are multiple variables matching one of the variable prefixes (e.g. t and te) then reading t would read any t and te files silently without warning.

Perhaps this issue showed up with the switch to 3 or 6 digit sequence numbers.

I believe this is the line at issue:

PsiPy/psipy/io/mas.py

Line 29 in f291894

return sorted(glob.glob(str(directory / f"{var}*")))

And maybe this one might need to be checked/revised for 3 vs 6 issues too:

PsiPy/psipy/io/mas.py

Line 119 in f291894

files = glob.glob(str(path / "*[0-9][0-9][0-9].*"))

I suspect a fix would be to be more stringent about the format, looking for either 3 digit or 6 digit HDF files separately and choosing one or the other (e.g. first look for f"{var}[0-9][0-9][0-9].h*" and if there are no matches then look for f"{var}[0-9][0-9][0-9][0-9][0-9][0-9].h*") but I'm not experienced enough with PsiPy IO to implement this knowing it won't cause side effects.