TST: indexes/test_base.py:TestIndex.test_format is flaky

[evectant]

indexes/test_base.py:TestIndex.test_format compares index.format() and str(index[0]), where index = Index([datetime.now()]). These won't match if the current timestamp ends with zeros:

In [2]: i = pd.Index([pd.Timestamp('2012-01-01 00:00:00.111111')])

In [3]: j = pd.Index([pd.Timestamp('2012-01-01 00:00:00.111000')])

In [4]: i.format(), [str(i[0])]
Out[4]: (['2012-01-01 00:00:00.111111'], ['2012-01-01 00:00:00.111111'])

In [5]: j.format(), [str(j[0])]
Out[5]: (['2012-01-01 00:00:00.111'], ['2012-01-01 00:00:00.111000'])

Same thing for real: https://travis-ci.org/pandas-dev/pandas/jobs/173440088#L1355

[jreback]

yeah this does occasionally fail

it's not a great test, but is testing the default behavior so no easy way to control the formatting
maybe put this in a while loop and get a new time if the current time ends with 000

put a short explanation there