'Test if save() bails when _prepare_save() returns False.'

def test_prepare_save(self, tmpdir, lineparser):

    (tmpdir / 'file').write('pristine\n')
    lineparser.data = ['changed']
    lineparser._prepare_save = (lambda : False)
    lineparser.save()
    assert ((tmpdir / 'file').read() == 'pristine\n')
