Ignore warning only on Python 3.4
This change to itersubclasses restores some determinism to it on Python 3.4.  See https://github.com/astropy/astropy/pull/1945#issuecomment-32522217

Conflicts:
	astropy/io/fits/util.py
Fix importing argparse on Python 2.6
Fix print_code_line to respect the UNICODE_OUTPUT configuration variable.
Fixed bug in Model2DKernel
Added type cast to float64 in CustomKernel and adapted peak normalization
Added simple ModelKernel tests
Clarified MexicanHatKernel normalization
Raising exception when normalizing kernels, that sum to zero.
Handle negative luminosity distances in distmod.

* Closes #2008
* Abs lum distances in distmod.
* Add unit test for this behavior.
Update test for non-unicode data
Merge pull request #1973 from mdboom/misc/python3.4-compat

Omnibus Python 3.4 compatibility fixes
Merge pull request #1988 from eteq/hmsdmsnamedtuple

Make hms/dms namedtuples and add `signed_dms`
Merge pull request #2007 from adonath/fixing_issue_#1986

Fixing #1986 and a few other minor issues
Merge pull request #2009 from aconley/negdist

Handle negative luminosity distances in distmod
Fixes issue 1912
Resolved a rebasing conflict in CHANGES.rst
Added regression test for issue #1912
Merge pull request #1912 from barentsen/fix-issue-1912

WCS.footprint_to_file() is broken
Fix astropy.utils.compat.argparse for Python 3.1