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.

str.encode, bytes.decode and bytearray.decode now use an
internal API to throw LookupError for known non-text encodings,
rather than attempting the encoding or decoding operation and
then throwing a TypeError for an unexpected output type.

The latter mechanism remains in place for third party non-text
encodings.

Backported changeset d68df99d7a57.

Patch by Arfrever Frehtes Taifersar Arahesis.

Patch by Arfrever Frehtes Taifersar Arahesis.