Fix TestReimportArchivedFiles.

This fix makes sure we check for a string where one
is expected and fixes the declaration of a method in library.py
(missing argument).

To test, make sure that http://ci.openmicroscopy.org/job/OMERO-5.0-merge-integration-python/ is green and in particular http://ci.openmicroscopy.org/job/OMERO-5.0-merge-integration-python/lastCompletedBuild/testReport/test.integration.test_reimport/TestReimportArchivedFiles/testConvertSynthetic/