cleanup: rename all iteritems methods to items and add iteritems alias Due to a quirk of our module importer setup on Python 3, all calls and definitions of methods named iteritems() get rewritten at import time. Unfortunately, this means there's not a good portable way to access these methods from non-module-loader'ed code like our unit tests. This change fixes that, which also unblocks test-manifest.py from passing under Python 3. We don't presently define any itervalues methods, or we'd need to give those similar treatment.