'compress_image does not fail when no file is provided.'

@mock.patch.object(settings._wrapped, 'OPTIPNG_PATH', '')
@mock.patch.object(kitsune.upload.tasks.subprocess, 'call')
def test_compress_no_file(self, call):

    image = ImageAttachment(content_object=self.obj, creator=self.user)
    compress_image(image, 'file')
    assert (not call.called)
