BF: explicit tuples in list comprehensions for 3.3

Python 3 needs explicit tuples in list comprehensions as in (2, 3)
rather than 2, 3.
BF: skip bz2 tests when bz2 mat save will fail

Python 3.3 has a bug in the bz2 implementation that means that released
versions of scipy will raise a ValueError when trying to save a mat file
to bz2.  Skip bz2 test when this will happen.