Issue #20791: copy.copy() now doesn't make a copy when the input is a bytes object.  Initial patch by Peter Otten.

Patch by Berker Peksag.

PathEntryFinder instances which only define find_module().

Reported by Yukihiro Nakadaira.

The signature and description of PyException_SetCause now use "cause"
rather than "ctx" to match the code.

For example: "finish_recv", not just "finish".

assert methods in coroutines.

It also simplify merges from Tulip to Trollius (Python 2 does not support non
local variables).

Use "from unittest import mock". It should simplify my work to merge new tests
in Trollius, because Trollius uses "mock" backport for Python 2.

This bug was of the major reasons for the release.

Adding missing docs for DynamicClassAttribute by copying the docstring.  The
doc entry could stand some expansion, which I will note on the issue.

Jason doced the change in the constructor *method* description, but
not the description of Request.method, so I added the change there
as well.

Also some fixups in the docs.

Also fix issue number in address sanity check entry.

Including the subsequent line re-wrapping.

Patch by Sean Rodman.