CI: use current versions for excel / dateutil / pytz on 3.4 build
Merge pull request #7170 from jreback/new

CI: use current versions for excel / dateutil / pytz on 3.4 build
CLN: Deprecation of assert_

#7131: Run s/self.assert_(/self.assertTrue( on remaining instances I can find. These were the multi-line expressions, and I tried to retain the formatting of the expressions
CLN: Deprecation of assert_

Fix formatting of one multi-line assertion, from assert_ --> assertTrue cleanup
Merge pull request #7172 from bwignall/issue7131_assert_

CLN: Deprecation of assert_
BUG: fix isnull for 0d object arrays
Merge pull request #7176 from shoyer/isnull-0d-object-array

BUG: fix isnull for 0d object arrays