In Python 3, dict.items() is already an iterator while dict.iteritems() no
longer exits. In Python 2, dict.items() is not an iterator but it works
and the small performance hit doesn't really matter for the salt config
pillar data which is really small.
Commit 2b51a6f0c3 introduced options for gitfs_remotes in a pillar by using a jinja test to see if a parameter is a mapping (dict etc.). This feature however is only available in jinja 2.6 or newer (see http://jinja.pocoo.org/docs/dev/templates/#mapping).
Although this version of Jinja is available on Ubuntu, other OS / package managers do provide older versions (2.2.1 in RedHat 6).
This change makes use of the "iterable" test which should do the exact same thing.