TST: more robust tests in HDFStore
should close #3069
will print additional output if this somehow fails, which I have never seen (except on travis)

Doing str(e) won't tell the exception type that was raised (IOError?)
and if the test doesn't fail, ti'll be difficult to find the build that contains the
debugging lead...
 I know but I have never seen it fail except a couple of times on Travis
and their is no reason it should fail (if the tests before didn't) except some sort of weird low level Pytables failure
which I suppose is possible
 Yeah, it looks solid. All the same, a failing test is trying to tell us something. it might
be travis wonkiness, it might be a data corruption bug. hemstringing the test
might end up hiding a real issue.
 is there a way in nose to easily show a warning of some kind?
 From the annoying nose of the "inplace=True" patch, I'm pretty sure
warnings from the warnings module are not suppressed by nose.

If you're going for a looping test run looking for the error.... I already did a 1000
and came up empty.
 there must be a very rare underlying error in PyTables that gets passed up which I am trapping and returning a top-level exception (related to IO)...
