Fix _PyBytesWriter API when Python is built in release mode with
assertions.

bpo-36389, bpo-38376: The _PyObject_CheckConsistency() function is
now also available in release mode. For example, it can be used to
debug a crash in the visit_decref() function of the GC.

Modify the following functions to also work in release mode:

* _PyDict_CheckConsistency()
* _PyObject_CheckConsistency()
* _PyType_CheckConsistency()
* _PyUnicode_CheckConsistency()

Other changes:

* _PyMem_IsPtrFreed(ptr) now also returns 1 if ptr is NULL
  (equals to 0).
* _PyBytesWriter_CheckConsistency() now returns 1 and is only used
  with assert().
* Reorder _PyObject_Dump() to write safe fields first, and only
  attempt to render repr() at the end.

Calling _Py_wfopen() is enough to check if filename is an existing
file or not. There is no need to check first isfile().

The "tmp" variable is no longer used.

The `required` argument to `argparse.add_subparsers` was added in #3027. This PR specifies the earliest version of Python where it is available.


https://bugs.python.org/issue26510



Automerge-Triggered-By: @merwok

KeyError should cause a failure in parsing the encoded word and should be caught and raised as a _InvalidEWError instead.

Add SMTPNotSupportedError in the exports of smtplib
Co-Authored-By: Brandt Bucher <brandtbucher@gmail.com>

* _Py_FindEnvConfigValue() now returns a string allocated
  by PyMem_RawMalloc().
* calculate_init() now decodes VPATH macro.
* Add calculate_open_pyenv() function.
* Add substring() and joinpath2() functions.

* Fix add_exe_suffix()

And a few cleanup changes.

* PyCalculatePath: add "_macro" to the 3 fields storing macro values
* Add dynamically allocated strings to PyCalculatePath

Revert the removal of PyThreadState_DeleteCurrent() with documentation.

On Windows use UTF-16 (or UTF-32 for 32-bit Tcl_UniChar) with the
"surrogatepass" error handler for converting to/from Tcl Unicode objects.

On Linux use UTF-8 with the "surrogateescape" error handler for converting
to/from Tcl String objects.

Converting strings from Tcl to Python and back now never fails
(except MemoryError).

* ismodule() no longer modify the input string.
* copy_absolute(), joinpath(): rename parameters and local variables.

Following symbolic links is now limited to 40 attempts, just to
prevent loops.

Add subfunctions:

* Add resolve_symlinks()
* Add calculate_argv0_path_framework()
* Add calculate_which()
* Add calculate_program_macos()

Fix also _Py_wreadlink(): readlink() result type is Py_ssize_t, not
int.

Replace "_PyRuntimeState" with "struct pyruntimestate" to avoid
a warning on typedef re-definition.

Replace "_PyRuntimeState" with "struct pyruntimestate" to avoid
a warning on typedef re-definition.

calculate_argv0_path() must read argv0_path link, not read
program_full_path link.

* Add log() method: add timestamp and load average prefixes
  to main messages.
* WindowsLoadTracker:

  * LOAD_FACTOR_1 is now computed using SAMPLING_INTERVAL
  * Initialize the load to the arithmetic mean of the first 5 values
    of the Processor Queue Length value (so over 5 seconds), rather
    than 0.0.
  * Handle BrokenPipeError and when typeperf exit.

* format_duration(1.5) now returns '1.5 sec', rather than
  '1 sec 500 ms'

The last line is now passed to the parser even if it does not end
with a newline, but only if it's a valid value.

WindowsLoadTracker.read_output() now uses a short buffer for
incomplete line.

Use forward declaration of types to avoid includes in the internal C
API. Add also comment to justify other includes.

test.pythoninfo now logs environment variables used by OpenSSL and
Python ssl modules, and logs attributes of 3 SSL contexts
(SSLContext, default HTTPS context, stdlib context).

* Fix TestWorkerProcess.__repr__(): start_time is only valid
  if _popen is not None.
* Fix _kill(): don't set _killed to True if _popen is None.
* _run_process(): only set _killed to False after calling
  run_test_in_subprocess().

bpo-37802, bpo-38321: Fix the following warnings:

    longobject.c(420): warning C4244: 'function': conversion from
    'unsigned __int64' to 'sdigit', possible loss of data

    longobject.c(428): warning C4267: 'function': conversion from
    'size_t' to 'sdigit', possible loss of data

On FreeBSD, Python no longer calls fedisableexcept() at startup to
control the floating point control mode. The call became useless
since FreeBSD 6: it became the default mode.

Fix the GCC warning: "initialization discards ‘const’ qualifier from
pointer target type".

* Windows: Fix counter name in WindowsLoadTracker. Counter names are
  localized: use the registry to get the counter name. Original
  change written by Lorenz Mende.
* Regrtest.main() now ensures that the Windows load tracker is also
  killed if an exception is raised
* TestWorkerProcess now ensures that worker processes are no longer
  running before exiting: kill also worker processes when an
  exception is raised.
* Enhance regrtest messages and warnings: include test name,
  duration, add a worker identifier, etc.
* Rename MultiprocessRunner to TestWorkerProcess
* Use print_warning() to display warnings.
Co-Authored-By: Lorenz Mende <Lorenz.mende@gmail.com>

PyConfig_InitPythonConfig() and PyConfig_InitIsolatedConfig() no
longer return PyStatus: they cannot fail anymore.