Add a note about pkgutil and how some things do not work in the face of PEP 302 permeating throughout import.

longer work as expected in Python 3.3 as importlib's loaders do not
implement the non-standard iter_modules() method. Also link to the
term "loader" in the requisite notes to help make it clearer what has
happened.

NotimplementedError when sys.implementation.cache_tag is None.

Thanks to Pranav Ravichandran for taking an initial stab at the patch.

importlib._bootstrap in imp to fix a grammatical mistake.

Thanks to Marc Abramowitz for the patch.

execfile().

Closes #15281, #15283: Don't make venv scripts executable, but copy source mode instead, and provide better help for pyvenv.

Issue 14814: The new systematic tests aren't just about error reporting any more - change names accordingly. Added and tweaked some example to ensure they were covering the intended code paths

issue 14826 - Address the buildbot failure quote of url is the required change ( explanation msg164973)

Patch by Brian Brazil.

Patch contributed by Stephen Thorne.

Patch contributed by Stephen Thorne.