no basestring in py3.5

[sbailey]

I'm confused about the following:

• specsim uses basestring several times, e.g. simulator.py line 46
• basestring doesn't exist in py3.5, so this code shouldn't work
• But py3.5 tests pass and coverage claims that it touched that line

desisim usage of specsim breaks under py3.5 because it does touch that line and ends with:

======================================================================
ERROR: test_quickgen (desisim.test.test_quickgen.TestQuickgen)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/sbailey/desi/git/desisim/build/lib/desisim/test/test_quickgen.py", line 191, in test_quickgen
    desisim.scripts.quickgen.main(opts)
  File "/Users/sbailey/desi/git/desisim/build/lib/desisim/scripts/quickgen.py", line 166, in main
    qsim = specsim.simulator.Simulator(args.config)
  File "/Users/sbailey/desi/git/specsim/specsim/simulator.py", line 46, in __init__
    if isinstance(config, basestring):
NameError: name 'basestring' is not defined

It's easy enough to fix the basestring usage in specsim, but we should take a moment to figure out why tests + coverage are tricking us on this one, thus I'm opening this issue instead of proceeding directly to a PR.

[weaverba137]

That is very strange. My initial guess was that basestring was being replaced with six.string_types with some astropy-affiliated magic, but I can't find any evidence for that.

[dkirkby]

I included use_2to3=True in setup.py, which I inherited from the astropy package template. This is supposed to run the 2to3 conversion when the package is installed in a python3 environment, including the basestring -> str substitution:

http://setuptools.readthedocs.io/en/latest/python3.html

I guess you didn't re-install when you switched from py2 to py3?

[weaverba137]

It might not even be a case of installing (in the python setup.py install sense); most DESI code will work even from a git checkout, provided environment variables are set correctly. I don't know if we want to require that for specsim, since it is technically a standalone package.

[sbailey]

Ben's guess is correct: I was using a "raw" checkout by just adding the top level directory to my PYTHONPATH without any "python setup.py install" or "python setup.py develop". I'll open a PR in a moment that converts the code to be genuinely py3 compatible rather than using 2to3 on-the-fly during install.