Fix PUP-1568 - no success variable anymore

In the refactoring within 000b8fef the success variables was
removed. So the error message shouldn't anymore use it.
Fix broken spec & wording of error message.

While working on 658f1237c1596a6f735b7b707130fc0897a1a113 I stumbled
accross another messages that would say 'with error code false', which
doesn't make a lot of sense. Also the plain 'expect raise_error' was
masking another problem with tests. One should always only look for the
exact expected error and not just general for any kind of error.
Merge pull request #2324 from duritong/fix/master/PUP-1568_fix_error_reporting

Fix/master/pup 1568 fix error reporting
(maint) Add Ruby 2.1.0 to Travis CI
Merge branch 'pr/2346'

* pr/2346:
  (maint) Add Ruby 2.1.0 to Travis CI

This closes GH-2346.