Test for API hidden apps.
Tests for returning only the non hidden projects.
Return only in listing calls authorized objects. Closes #843
Fix rev head.
Specifying the exceptions classes, otherwise raise it.
Exclude last except from coverage.
Merge pull request #904 from PyBossa/issue-843-hidden-apps-api

Issue 843 hidden apps api
Merge branch 'master' into issue-repositories

* master:
  Exclude last except from coverage.
  Specifying the exceptions classes, otherwise raise it.
  Fix rev head.
  Return only in listing calls authorized objects. Closes #843
  Tests for returning only the non hidden projects.
  Test for API hidden apps.

Conflicts:
	pybossa/api/api_base.py