Docs: remove link elements in builders other than HTML

[m-aciek]

Follow-up for #132220 (comment)). This change fixes EPUB builds. epubcheck after this change results in 25 fewer errors. Could we please backport it for supported versions?

Before:

% uvx epubcheck 2>&1 >/dev/null | grep 'FATAL'
FATAL - RSC-016 - Python.epub/about.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/bugs.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/abstract.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/allocation.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/apiabiversion.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/arg.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/bool.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/buffer.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/bytearray.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/bytes.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/call.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/capsule.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/cell.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/code.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/codec.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/complex.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/concrete.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/c-api/contextvars.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/contents.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/copyright.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/download.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/glossary.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/index.xhtml:26:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/license.xhtml:27:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".
FATAL - RSC-016 - Python.epub/py-modindex.xhtml:29:5 - Fatal Error while parsing file: The element type "link" must be terminated by the matching end-tag "</link>".

After:

---

📚 Documentation preview 📚: https://cpython-previews--133720.org.readthedocs.build/

[hugovk]

We have three conditionals in a row (extra whitespace for clarity):

    {% if builder == "html" and enable_analytics %}
      <script defer data-domain="docs.python.org" src="https://analytics.python.org/js/script.outbound-links.js"></script>
    {% endif %}
 
   {% if builder == "html" %}<link rel="canonical" href="https://docs.python.org/3/{{pagename}}.html">{% endif %}
 
   {% if builder != "htmlhelp" %}
      {% if pagename == 'whatsnew/changelog' and not embedded %}
      <script type="text/javascript" src="{{ pathto('_static/changelog_search.js', 1) }}"></script>{% endif %}
    {% endif %}

Should that last if builder != "htmlhelp" also be if builder == "html"?

If so, shall we factor that check out? Something along the lines of:

    {% if builder == "html" %}

      {% if enable_analytics %}
        <script defer data-domain="docs.python.org" src="https://analytics.python.org/js/script.outbound-links.js"></script>
      {% endif %}

      <link rel="canonical" href="https://docs.python.org/3/{{pagename}}.html">
 
      {% if pagename == 'whatsnew/changelog' and not embedded %}
      <script type="text/javascript" src="{{ pathto('_static/changelog_search.js', 1) }}"></script>{% endif %}

    {% endif %}

[merwok]

@Yhg1s this fixes a bug in docs epub build; would it be acceptable for backport to 3.12 ?

[Yhg1s]

Yeah, backporting to 3.12 is fine.

[miss-islington-app]

Thanks @merwok for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12, 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

3.14 branch.

[bedevere-app]

3.13 branch.

[bedevere-app]

3.12 branch.