Python: bump minimum sphinx version to 3.4.3

With RHEL 8 support retired (It's been two years since RHEL9 released),
our very oldest build platform version of Sphinx is now 3.4.3; and
keeping backwards compatibility for versions as old as v1.6 when using
domain extensions is a lot of work we don't need to do.

This patch is motivated by my work creating a new QAPI domain, which
unlike the dbus documentation, cannot be allowed to regress by creating
a "dummy" doc when operating under older sphinx versions. Easier is to
raise our minimum version as far as we can push it forwards, reducing my
burden in creating cross-compatibility hacks and patches.

A sampling of sphinx versions from various distributions, courtesy
https://repology.org/project/python:sphinx/versions

Alpine 3.16: v4.3.0 (QEMU support ended 2024-05-23)
Alpine 3.17: v5.3.0
Alpine 3.18: v6.1.3
Alpine 3.19: v6.2.1
Ubuntu 20.04 LTS: EOL
Ubuntu 22.04 LTS: v4.3.2
Ubuntu 22.10: EOL
Ubuntu 23.04: EOL
Ubuntu 23.10: v5.3.0
Ubuntu 24.04 LTS: v7.2.6
Debian 11: v3.4.3 (QEMU support ends 2024-07-xx)
Debian 12: v5.3.0
Fedora 38: EOL
Fedora 39: v6.2.1
Fedora 40: v7.2.6
CentOS Stream 8: v1.7.6 (QEMU support ended 2024-05-17)
CentOS Stream 9: v3.4.3
OpenSUSE Leap 15.4: EOL
OpenSUSE Leap 15.5: 2.3.1, 4.2.0 and 7.2.6

RHEL9 / CentOS Stream 9 becomes the new defining factor in staying at
Sphinx 3.4.3 due to downstream offline build requirements that force us
to use platform Sphinx instead of newer packages from PyPI.

Signed-off-by: John Snow <jsnow@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-id: 20240703175235.239004-2-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

docs/conf.py

@@ -53,10 +53,9 @@
 
 # If your documentation needs a minimal Sphinx version, state it here.
 #
-# Sphinx 1.5 and earlier can't build our docs because they are too
-# picky about the syntax of the argument to the option:: directive
-# (see Sphinx bugs #646, #3366).
-needs_sphinx = '1.6'
+# 3.4.3 is the oldest version of Sphinx that ships on a platform we
+# pledge build support for.
+needs_sphinx = '3.4.3'
 
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom

pythondeps.toml

@@ -23,7 +23,7 @@ meson = { accepted = ">=1.1.0", installed = "1.2.3", canary = "meson" }
 
 [docs]
 # Please keep the installed versions in sync with docs/requirements.txt
-sphinx = { accepted = ">=1.6", installed = "5.3.0", canary = "sphinx-build" }
+sphinx = { accepted = ">=3.4.3", installed = "5.3.0", canary = "sphinx-build" }
 sphinx_rtd_theme = { accepted = ">=0.5", installed = "1.1.1" }
 
 [avocado]