This is just a technical prototype to measure and discuss the impact and
implication of moving to C++ for kernel code generation.

* replace superfluous single-character regex character
classes with their literal string equivalents; this
avoids the overhead associated with a character class
when there's only a single character enclosed (so there's
no benefit to the class overhead)

* for more information see:
Chapter 6 of:
Friedl, Jeffrey. Mastering Regular Expressions. 3rd ed.,
O’Reilly Media, 2009.

* Cleanup unused imports (F401) of mostly standard Python modules,
  or some internal but unlikely referenced modules
* Where internal imports are potentially used, mark with noqa
* Avoid redefinition of imports (F811)

As numpy is Python 3 only, these import statements are now unnecessary
and don't alter runtime behavior.

Currently numpy.distutils.Extension class subclasses python's
distutils.extension.Extension class and initializes the base class with
a call that uses positional arguments rather than keyword arguments.
This causes problems with setuptools 25.4.0 where the Extension class
gets a new init function that expects keyword rather than positional
arguments. We should have been using keyword arguments all along and our
luck has run out, so use proper keywords

Closes #7951.

Run the 2to3 ws_comma fixer on *.py files. Some lines are now too long
and will need to be broken at some point. OTOH, some lines were already
too long and need to be broken at some point. Now seems as good a time
as any to do this with open PRs at a minimum.

Now is as good a time as any with open PR's at a low.