fix sorting in _sort_iterate_resultset in py3

[pbauer]

No description provided.

[tseaver]

@pbauer Is there an issue number we should be closing with this PR? Or linking from another repo?

[icemac]

At least an change log entry would be nice.

[pbauer]

I added a changenote. Sorry, there is no issue to reference. One of the many failing test is testAllObjectsHaveOrder in CMFPlone:

Traceback (most recent call last):
  File "/srv/python3.6/lib/python3.6/unittest/case.py", line 59, in testPartExecutor
    yield
  File "/srv/python3.6/lib/python3.6/unittest/case.py", line 605, in run
    testMethod()
  File "/home/jenkins/workspace/plip-py3/src/Products.CMFPlone/Products/CMFPlone/tests/testCatalogTool.py", line 854, in testAllObjectsHaveOrder
    sorted_objs = self.catalog(sort_on='getObjPositionInParent')
  File "/home/jenkins/workspace/plip-py3/src/Products.CMFPlone/Products/CMFPlone/CatalogTool.py", line 469, in searchResults
    return ZCatalog.searchResults(self, query, **kw)
  File "/home/jenkins/workspace/plip-py3/src/Products.ZCatalog/src/Products/ZCatalog/ZCatalog.py", line 612, in searchResults
    return self._catalog.searchResults(query, **kw)
  File "/home/jenkins/workspace/plip-py3/src/Products.ZCatalog/src/Products/ZCatalog/Catalog.py", line 1088, in searchResults
    return self.search(query, sort_indexes, reverse, sort_limit, _merge)
  File "/home/jenkins/workspace/plip-py3/src/Products.ZCatalog/src/Products/ZCatalog/Catalog.py", line 704, in search
    actual_result_count=rlen, b_start=b_start, b_size=b_size)
  File "/home/jenkins/workspace/plip-py3/src/Products.ZCatalog/src/Products/ZCatalog/Catalog.py", line 1008, in sortResults
    second_indexes_key_map)
  File "/home/jenkins/workspace/plip-py3/src/Products.ZCatalog/src/Products/ZCatalog/Catalog.py", line 794, in _sort_iterate_resultset
    result.sort(reverse=reverse)
TypeError: '<' not supported between instances of 'NoneType' and 'int'

See https://jenkins.plone.org/view/PLIPs/job/plip-py3/766/consoleText for more failing tests.

[icemac]

LGTM.