Merge pull request #16 in CASA/casaviewer from CAS-13429 to master
* commit 'a583a3ebd78a39199dd460f8417a36a6ec300b06':
CAS-13429: test_msview - non-linux requires gui=True in casa 6, add exception test, clarify wording of exception in viewertool
Fixed that path to the test data to point to the new casatestdata repository