Updated www/py-pelican to 4.2.0.

Upstream changes:

3.7.1 to 4.0:
* Replace develop_server.sh script with pelican --listen
* Improved copy/link behavior for large static files (e.g., videos)
* New {static} syntax to link to static content; content linked to by
* {static} and {attach} is automatically copied over even if not in
* STATIC_PATHS
* Pages can now have draft status
* Show current settings via new --print-settings flag
* New signals: feed_generated and page_generated_write_page
* Replace Fabric with Invoke and fabfile.py template with tasks.py
* New ARTICLE_TRANSLATION_ID and PAGE_TRANSLATION_ID settings to
* specify metadata attributes used to identify/disable translations
* HTML reader now parses multiple occurrences of metadata tags as a list
* New Blogger XML backup importer
* Wordpress importer now updates file links to point to local copies if the
* files were downloaded with --wp-attach.
* Many bug fixes, tweaks, and other enhancements

4.0 to 4.0.1:
* Refactor pelican.server logging
* Fix bug in which all static files were processed as "draft"
* Bug fixes for Invoke/Makefile automation, Importer, and other miscellanea

4.0.1 to 4.1:
* Live browser reload upon changed files (provided via Invoke task)
* Add pyproject.toml, managed by Poetry
* Support for invoking python -m pelican
* Add relative source path attribute to content
* Allow directories in EXTRA_PATH_METADATA
* Add all_articles variable to period pages (for recent posts functionality)
* Improve debug mode output
* Remove blank or duplicate summaries from Atom feed
* Fix bugs in pagination, pelican-import, pelican-quickstart, and feed importer

4.1 to 4.1.1:
* Add AutoPub to auto-publish releases on PR merge
* Add CSS classes for reStructuredText figures
* Pass argv to Pelican main entrypoint
* Set default content status to a blank string rather than None

4.1.1 to 4.1.2:
* Fix pelican.settings.load_source to avoid caching issues

4.1.2 to 4.1.3:
* Fix quick-start docs regarding pelican --listen
* Set default listen address to 127.0.0.1
* Add extra/optional Markdown dependency to setup.py
* Use correct SSH port syntax for rsync in tasks.py
* Place all deprecated settings handling together
* Add related project URLs for display on PyPI
* Skip some tests on Windows that can't pass due to filesystem differences

4.1.3 to 4.2.0:
* Support inline SVGs; don't treat titles in SVGs as HTML titles
* Add category to feeds (in addition to tags)
* Improve content metadata field docs
* Add docs for including other Markdown/reST files in content

Pkgsrc changes:
* updated the way software version is brought to the documentation (upstream
imports it from the software, but this prevents from building the package)

(nils)