Log Message:
Updated py-foolscap to 0.12.6.

* Release 0.12.6 (12-Jan-2017)

This is a minor release to improve compatibility with Twisted and I2P.

In this release, the Foolscap test suite no longer uses several deprecated
and/or internal Twisted attributes, so it should pass cleanly on the next
release of Twisted (which will probably be named Twisted-17.0.0).

In addition, the I2P connection handler was enhanced to let applications pass
arbitrary kwargs through to the underlying "SAM" API.

Finally connection-status error messages should be slightly cleaner and
provide more useful information in the face of unrecogized exceptions.