Fix test: ValueErrors have no .message in Python 3
Fix test: ValueErrors have no .message in Python 3

skyfielders/python-skyfield,GuidoBR/python-skyfield,ozialien/python-skyfield,ozialien/python-skyfield,exoanalytic/python-skyfield,exoanalytic/python-skyfield,GuidoBR/python-skyfield,skyfielders/python-skyfield