Update old syntax

[bamford]

Hi Ken!

I've got some students using smpy to generate SEDs for simulated galaxies. It seems to be working fine, but they encountered some issues when the code couldn't find required files. The main thing was some outdated Exception syntax. Anyway, I took a look and have ended up having a go at minimally modernising the code:

• I used 2to3 to fixed old Python 2 syntax (the Exception thing and a few print statements)
• The code was printing some repeated numpy and h5py deprecation warnings, so I fixed those
• For the hell of it I applied pyupgrade --py3-plus, which mostly tidied up some .format statements and removed use of xrange.
• I added an error message if no filter files can be found.

So, here's my version in case you want to merge the changes in to your repo.

[dunkenj]

Hi Steven,
Amazing, thanks. I should be able to fold everything in next week.