#18856: improve test coverage of the calendar module.  Patch by Madison May.
Fix tkinter regression introduced by the security fix in #16248.
Merge heads.
Issue #19018: The heapq.merge() function no longer suppresses IndexError
Null merge of 3.1 into 3.2

Changeset c39f42f46a05 left a dangling head on 3.1.
Null merge of 3.2 into 3.3.