BUG: compat_pickle should not modify global namespace
CLN: PEP8 cleanup of the io module
Merge pull request #5661 from jreback/pickle_fix

BUG: compat_pickle should not modify global namespace
DOC: add pickle compat warning to docs
Merge pull request #5667 from jreback/docs

DOC: add pickle compat warning to docs
Merge pull request #5663 from alefnula/pep8

CLN: PEP8 cleanup of the io module