setUp must be called on a fixture's parent first

There is some odd behavior when a fixture's setUp fails before it has a
change to call the parent's setUp. It causes an error in the error
handling and the original exception is lost. The bug has been reported
upstream:
  https://bugs.launchpad.net/python-fixtures/+bug/1299502

Change-Id: I27cbfbe2c8ae34e72950361f8d0d7d8d3e249f8c
Merge "setUp must be called on a fixture's parent first"