Remove Python 2 leftovers.

[icemac]

Fixes #236.

[coveralls]

Pull Request Test Coverage Report for Build 6954724829

• 8 of 13 (61.54%) changed or added relevant lines in 9 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 73.535%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/ZEO/StorageServer.py	1	2	50.0%
src/ZEO/runzeo.py	0	1	0.0%
src/ZEO/tests/testZEOOptions.py	0	1	0.0%
src/ZEO/scripts/zeoqueue.py	0	2	0.0%

Totals
Change from base Build 6927399081:	0.06%
Covered Lines:	7795
Relevant Lines:	10121

---

💛 - Coveralls

[dataflake]

If you want to make a 6.0 release the pypy test failures should be fixed first.

[d-maurer]

The failing PyPy3 checks result from a buggy IterationTest.checkIteratorGCStorageTPCAborting test. The test creates an iterator causing an entry in the WeakValueDict _iterators and the set _iterator_ids. The iterator reference is not stored; this means that the iterator can be garbage collected immediately. The test failure is caused because _iterators has less elements than iterator_ids which happens when there has meanwhile been a garbage collection. _assertIteratorIdsEmpty tries to prevent such a race condition by a call to gc.disable() but this can be too late. A fix would be to disable garbage collection before the iterator is created.

[icemac]

Thank you for reviewing this PR. 😃