Update idna to 3.20

[pyup-bot]

This PR updates idna from 3.11 to 3.20.

Changelog

3.20

- Update to Unicode 18.0.0.
- Better enforcement of the domain length limit in the incremental
codec.
- Add support for Python 3.15.

3.19

- Restore the `std3_rules` option, which had no effect since changes
to UTS 46 processing in Unicode 16. Note that `uts46_remap()`
defaults to enabling STD3 rules, so direct callers will see input
containing non-LDH ASCII characters rejected again.
- Performance improvements to UTS 46 mapping, particularly for
ASCII-only domains.
- Test on free-threaded CPython with the GIL disabled and document
thread safety.
- Expose the Unicode version of the generated tables as
`idna.unicode_version`, and show it in `idna --version`.
- Add `code`, `text`, `codepoint` and `position` attributes to
`IDNAError` so that the failed rule and the offending character can
be identified without parsing the exception message.
- The deprecated `transitional` argument to `encode()` and
`uts46_remap()` is now completely ignored, and gives a deprecation warning
for the latter.
- Reject A-labels that are not the canonical Punycode encoding of
their U-label.
- Fix CONTEXTJ violations raising `IDNAError` instead of
`InvalidCodepointContext`.
- Consistently raise `IDNAError` for empty labels and non-ASCII bytes
passed to label helper functions and the incremental codec.
- Add property-based tests, extended fuzzing targets, coverage
measurement, and CI checks that the data tables match the generator
output.
- Various code quality and tooling improvements.

Thanks to stefan6419846, LouieLuNZ, and Salvatore Corvaglia for
contributions to this release.

3.18

- When decoding a domain, add a `display` argument that will pass
through invalid labels rather than raising an exception.

3.17

- Substantial 75% reduction in memory usage through new data
structures and some optimization in processing speed.
- Added a general 1024-character input length cap to the public
validation, conversion, and codec entry points. This is well above
any legitimate domain or label and guards against pathological
inputs.

3.16

- Add a command-line interface (`python -m idna`, also available as
the `idna` script). Encodes or decodes one or more domains supplied
as arguments or on standard input, with options to select A-label
or U-label output and control error handling.
- Raise the minimum supported Python version to 3.9
- Various code quality improvements

3.15

- Enforce DNS-length cap on individual labels early in `check_label`,
short-circuiting contextual-rule processing for oversized input
while staying compatible with UTS 46 usage.
- Tidy core helpers: hoist bidi category sets to module-level
frozensets (avoiding per-codepoint list construction), simplify
length checks, and reuse the shared `_unicode_dots_re` from
`idna.core` in the codec module.
- Use `raise ... from err` for proper exception chaining and
switch internal string formatting to f-strings.
- Allow `flit_core` 4.x in the build backend.
- Expand the ruff lint set (flake8-bugbear, flake8-simplify,
pyupgrade, perflint) and apply the surfaced fixes; pin lint CI
to Python 3.14.
- Add Dependabot configuration for GitHub Actions.
- Convert README and HISTORY from reStructuredText to Markdown.
- Reference CVE-2026-45409 for the 3.14 advisory in place of the
initial GHSA identifier.

Thanks to Felix Yan, Stan Ulbrych, and metsw24-max for
contributions to this release.

3.14

- Removed opportunity to process long inputs into quadratic
time by rejecting oversize inputs up-front. Closes a bypass
of the CVE-2024-3651 mitigation. [CVE-2026-45409]

Thanks to Stan Ulbrych for reporting the issue.

3.13

- Correct classification error for codepoint U+A7F1

3.12

- Update to Unicode 17.0.0.
- Issue a deprecation warning for the transitional argument.
- Added lazy-loading to provide some performance improvements.
- Removed vestiges of code related to Python 2 support, including
segmentation of data structures specific to Jython.

Thanks to Rodrigo Nogueira for contributions to this release.

Links

• PyPI: https://pypi.org/project/idna
• Changelog: https://data.safetycli.com/changelogs/idna/