pass exception instance instead of string to Failure

This fixes a DeprecationWarning like this:

    /usr/lib64/python2.6/site-packages/twisted/internet/defer.py:267: DeprecationWarning: Don't pass strings (like 'Timeout') to failure.Failure (replacing with a DefaultException).
      fail = failure.Failure(fail)

Change-Id: I369988a0e44441399df032f6489a7d1578b05c71
Merge "pass exception instance instead of string to Failure" into develop
ControlGroup configuration option no longer valid.

See: https://lwn.net/Articles/555922/

Bug: 1001304
Add a release note generator

Manually filled in the release notes for 0.6.47-1

Change-Id: I5df739717586bcac028490a5f2beb92c4c8bc0d5
Automatic commit of package [beah] release [0.6.48-1].