[PATCH 095/153] Add os.path.isfile() check for pex zip_safe=False mode to unbreak pants py.
[PATCH 095/153] Add os.path.isfile() check for pex zip_safe=False mode to unbreak pants py.

RB_ID=207374

(sapling split of 6f67cef6ebddf29343c574bf3934378c38b65fc2)

(sapling split of ff01f03de9345122fa0d3b5d19a974a00109b47d)
jsirois/pex,snyaggarwal/pex,mzdanieltest/pex,kwlzn/pex,kwlzn/pex,snyaggarwal/pex,mzdanieltest/pex,pantsbuild/pex,jamesbroadhead/pex,pantsbuild/pex,URXtech/pex,jamesbroadhead/pex,URXtech/pex,pombredanne/pex,rouge8/pex,sixninetynine/pex,jsirois/pex,pombredanne/pex,rouge8/pex,sixninetynine/pex