Fixes:
* Unused import
* Redundant backslash
* Use of discouraged if not x in y
* Use of deprecated form of raising exceptions
Follow-up to PR #655 as requested by @gribozavr
This makes it clearer via their name what the two scripts are meant to
be used for.
As a recap:
1. pipeline_generator.py is meant for generating pass pipeline json
files.
2. pipelines_build_script.py is a script built ontop of
pipeline_generator.py that makes it easy to run build-script with
various pass pipelines that can be generated from
pipeline_generator.py. It is meant to be used on buildbots and for ones
own enjoyment as well.
Swift SVN r24315
