Update pyenv and default python version.

edx-platform is building and running with Python 3.12 so tutor main
should follow suit. This change should not be backported to release at
this time. Python 3.12 will be the default version of Python for
edx-platform in Verawood.

Author: feanil

changelog.d/20260121_123520_feanil_patch_2.md

@@ -0,0 +1,13 @@
+<!--
+Create a changelog entry for every new user-facing change. Please respect the following instructions:
+- Indicate breaking changes by prepending an explosion 💥 character.
+- Prefix your changes with either [Bugfix], [Improvement], [Feature], [Security], [Deprecation].
+- You may optionally append "(by @<author>)" at the end of the line, where "<author>" is either one (just one)
+  of your GitHub username, real name or affiliated organization. These affiliations will be displayed in
+  the release notes for every release.
+-->
+
+<!-- - 💥[Feature] Foobarize the blorginator. This breaks plugins by renaming the `FOO_DO` filter to `BAR_DO`. (by @regisb) -->
+<!-- - [Improvement] This is a non-breaking change. Life is good. (by @billgates) -->
+
+[Improvement] Update to use Python 3.12 for edx-platform

tutor/templates/build/openedx/Dockerfile

@@ -29,9 +29,9 @@ RUN --mount=type=cache,target=/var/cache/apt,sharing=locked \
 # Install pyenv
 # https://www.python.org/downloads/
 # https://github.com/pyenv/pyenv/releases
-ARG PYTHON_VERSION=3.11.8
+ARG PYTHON_VERSION=3.12.12
 ENV PYENV_ROOT=/opt/pyenv
-RUN git clone https://github.com/pyenv/pyenv $PYENV_ROOT --branch v2.3.36 --depth 1
+RUN git clone https://github.com/pyenv/pyenv $PYENV_ROOT --branch v2.6.18 --depth 1
 
 # Install Python
 RUN $PYENV_ROOT/bin/pyenv install $PYTHON_VERSION