use python 3.12.8

this includes/bundles a non-broken pip for old macOS. #8495

Vagrantfile

@@ -214,7 +214,7 @@ def install_pythons(boxname)
   return <<-EOF
     . ~/.bash_profile
     echo "PYTHON_CONFIGURE_OPTS: ${PYTHON_CONFIGURE_OPTS}"
-    pyenv install 3.12.4  # tests, binary build (3.12.5/6/7 has a broken pip on old macOS)
+    pyenv install 3.12.8
     pyenv rehash
   EOF
 end
@@ -232,8 +232,8 @@ def build_pyenv_venv(boxname)
     . ~/.bash_profile
     cd /vagrant/borg
     # use the latest 3.12 release
-    pyenv global 3.12.4
-    pyenv virtualenv 3.12.4 borg-env
+    pyenv global 3.12.8
+    pyenv virtualenv 3.12.8 borg-env
     ln -s ~/.pyenv/versions/borg-env .
   EOF
 end
@@ -279,8 +279,8 @@ def run_tests(boxname, skip_env)
     . ../borg-env/bin/activate
     if which pyenv 2> /dev/null; then
       # for testing, use the earliest point releases of the supported python versions:
-      pyenv global 3.12.4
-      pyenv local 3.12.4
+      pyenv global 3.12.8
+      pyenv local 3.12.8
     fi
     # otherwise: just use the system python
     # some OSes can only run specific test envs, e.g. because they miss FUSE support: