Python 3: use items() instead of iteritems()

iteritems was removed in Python 3 because items returns a view object.

Traceback (most recent call last):
  File "../../bin/compare-source-package-list", line 1163, in <module>
    files, patches, links, new = process_sources(source_entries, lists_dir)
  File "../../bin/compare-source-package-list", line 1141, in process_sources
    actions = check_source_package(source_entry, srcpkg)
  File "../../bin/compare-source-package-list", line 1019, in check_source_package
    info = get_info(srcpkg)
  File "../../bin/compare-source-package-list", line 484, in get_info
    dsc_hash_type, dsc_hash =  [(k, v) for k, v in dsc.iteritems() if k not in ('name', 'size')][0]
AttributeError: 'Deb822Dict' object has no attribute 'iteritems'