[rtags] Allow to 'derive' rtags Since some releases, rtags (structure underlying uicfg) have selector and may be copied using something like: new_rtags = deepcopy(original_rtags) new_rtags.__module__ = __name__ new_rtags.__select__ = custom_selector The problem is that starting from that, both rtags wil diverge and changes in original_rtags won't be considered, while we usually want to set a few specific rules only in new_rtags. To fix this problem, this cset introduces the notion of "derivated/parent" rtag, eg: new_rtags = original_rtags.derive(__name__, custom_selector) Beside easier copying, when using the above method changes in original_rtags which are not overriden by new_rtags will be considered since it only hold its specific rules but look among its parent chain for non-found keys. Along the way, flake8 unittest_rtags. Closes #16164880

import unittest

from cubicweb.web import http_headers


class TestGenerators(unittest.TestCase):
    def test_generate_true_false(self):
        for v in (True, 1, 'true', 'True', 'TRUE'):
            self.assertEqual('true', http_headers.generateTrueFalse(v))
        for v in (False, 0, 'false', 'False', 'FALSE'):
            self.assertEqual('false', http_headers.generateTrueFalse(v))

        with self.assertRaises(ValueError):
            http_headers.generateTrueFalse('any value')

if __name__ == '__main__':
    from unittest import main
    main()