This is a perfect example of LBYL going wrong: that code could be executed
by several workers in parallel, and os.mkdir() attempted on the same
path by multiple processes.

coverage.py reports 99% on branch coverage, but that appears to be
a bug or limitation in coverage.py.

Issue #5057: fix a bug in the peepholer that led to non-portable pyc files between narrow and wide builds while optimizing BINARY_SUBSCR on non-BMP chars (e.g. "\U00012345"[0]).

Issue #11467: Fix urlparse behavior when handling urls which contains scheme specific part only digits.

#11845: Fix typo in rangeobject.c that caused a crash in compute_slice_indices.  Patch by Daniel Urban.