'A ``PathError`` is raised if the path given to
``RootCredential.from_path`` does not exist.'

def test_load_error_on_non_existent_path(self):

    path = FilePath(self.mktemp())
    e = self.assertRaises(PathError, RootCredential.from_path, path)
    expected = 'Unable    to    load    certificate    authority    file.    Please    run    `flocker-ca    initialize`    to    generate    a    new    certificate    authority.    No    such    file    or    directory    {path}'.format(path=path.child(AUTHORITY_CERTIFICATE_FILENAME).path)
    self.assertEqual(str(e), expected)
