Patch by David Dudson.

Patch by Stephen J. Turnbull.

Issue #28105.

is now part of the official flags.

Also provide a sample Install Certificates command script to install a
set of root certificates from the third-party certifi module.

Issue #27213.

Revert change "Issue #27213: Reintroduce checks in _PyStack_AsDict()", pushed
by mistake.

It seems like at least 2 buildbots need more than 15 minutes per test file.
Example with "AMD64 Snow Leop 3.x":

    10 slowest tests:
    - test_tools: 14 min 40 sec
    - test_tokenize: 11 min 57 sec
    - test_datetime: 11 min 25 sec
    - ...

Issue #27744:

* Release msg.msg_iov memory block.
* Release memory on PyMem_Malloc(controllen) failure

Issue #27744:

* PEP 7: add {...} around if blocks
* assign variables and then check their value in if() to make the code easier
  to read and to debug.