ana_scans.py doesn't fail if one of the subcommand fails

[lmoureaux]

Brief summary of issue

ana_scans.py invokes other commands such as anaUltraScurve.py. However, ana_scans.py doesn't notice when one of those commands fails, and will happily keep running. ana_scans.py will exit with status code zero even if somewhat went horribly wrong. It should instead follow the usual conventions and return a non-zero status code.

Types of issue

• Bug report (report an issue with the code)
• Feature request (request for change which adds functionality)

Expected Behavior

If one of the subcommands fails, I expect ana_scans.py to at least report a non-zero status code.

Current Behavior

The status code is always zero (except maybe when killed).

Context (for feature requests)

Was trying to use ana_scans.py to setup unit tests on Travis (see #27).

Your Environment

• Version used: master, master prior to bug Fitting is broken #24 got fixed
• Python version: 2.6.x, 2.7.x
• More details in [RFC] Integrate gem-plotting-tools with Travis CI #27