Wrap subscription.js call with try/except

PEP8 updates
Revert "Wrap subscription.js call with try/except"

This reverts commit 48dc390ef5ee907fa60c761da970e8a6d69c8647.
Wrap subscription.js call with try/except
Added unittest for subscription error
Merge pull request #145 from sdelements/rally_fix_pt_58170364

Wrap subscription.js call with try/except