Convert dospath test suite to PyUnit, adding a couple more cases for isabs() (no false results were checked) and splitdrive().
Convert dospath test suite to PyUnit, adding a couple more cases for
isabs() (no false results were checked) and splitdrive().

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator