Issue #28056 and issue #26058.

by the user.

It turns out we can't depend on email.message getting imported every place
message_factory is needed, so to avoid a circular import we need to special
case Policy.message_factory=None in the parser instead of using monkey
patching.  I had a feeling that was a bad idea when I did it.

generalizations added in 3.5.

Issue #27810:

* Modify vgetargskeywordsfast() to work on a C array of PyObject* rather than
  working on a tuple directly.
* Add _PyArg_ParseStack()
* Argument Clinic now emits code using the new METH_FASTCALL calling convention

Issue #27810: Add a new calling convention for C functions:

    PyObject* func(PyObject *self, PyObject **args,
                   Py_ssize_t nargs, PyObject *kwnames);

Where args is a C array of positional arguments followed by values of keyword
arguments. nargs is the number of positional arguments, kwnames are keys of
keyword arguments. kwnames can be NULL.

Issue #28040: Fix _PyDict_DelItem_KnownHash() and _PyDict_Pop(): convert
splitted table to combined table to be able to delete the item.

Write an unit test for the issue.

Patch by INADA Naoki.

Patch by Jason Fried.

Issue 27948: Allow backslashes in the literal string portion of f-strings, but not in the expressions. Also, require expressions to begin and end with literal curly braces.

Why do we have two sysconfig modules again?

generalizations added in 3.5.

Tested on macOS 10.11 dtrace, Ubuntu 16.04 SystemTap, and libbcc.

Largely based by an initial patch by Jesús Cea Avión, with some
influence from Dave Malcolm's SystemTap patch and Nikhil Benesch's
unification patch.

Things deliberately left out for simplicity:
- ustack helpers, I have no way of testing them at this point since
they are Solaris-specific
- PyFrameObject * in function__entry/function__return, this is
SystemTap-specific
- SPARC support
- dynamic tracing
- sys module dtrace facility introspection

All of those might be added later.