Fixes a bug that caused the use of _as_mpl_axes to crash if one of the returned axes arguments defined __getitem__ but was not iterable.
PEP8 fixes
Call to iterable(v) is redundant - can just try and convert to a tuple directly
Merge pull request #3196 from astrofrog/issue-3196

Issue with iterability of axes arguments [backport to 1.4.x]