Log Message:
py-diffoscope: update to 226

Changes since 224:

[ Christopher Baines ]
* Add an lzip comparator with tests.

[ Chris Lamb ]
* Add support for comparing the "text" content of HTML files using \ 
html2text.
  (Closes: #1022209, reproducible-builds/diffoscope#318)
* Misc/test improvements:
  * Drop the ALLOWED_TEST_FILES test; it's mostly just annoying.
  * Drop other copyright notices from lzip.py and test_lzip.py.
  * Use assert_diff helper in test_lzip.py.
  * Pylint tests/test_source.py.

[ Mattia Rizzolo ]
* Add lzip to debian dependencies.

[ Chris Lamb ]
* Add support for detecting ordering-only differences in XML files.
  (Closes: #1022146)
* Fix an issue with detecting ordering differences. (Closes: #1022145)
* Add support for ttx(1) from fonttools.
  (Re: reproducible-builds/diffoscope#315)
* Test improvements:
  - Tidy up the JSON tests and use assert_diff over get_data and manual
    assert in XML tests.
  - Rename order1.diff to json_expected_ordering_diff for consistency.
  - Temporarily allow the stable-po pipeline to fail in the CI.
* Use consistently capitalised "Ordering" everywhere we use the word in
  diffoscope's output.