WIP: Use python 3.9 with opt-out option on centos8

Change-Id: Id41fd6aba60ccf9f14c332a82de533546d25b518

dib/ironic-python-agent-ramdisk/environment.d/20-ipa-distro-family.bash

@@ -9,6 +9,14 @@ if [[ ${DISTRO_NAME} =~ (centos|rhel) && ${DIB_RELEASE%-stream} > 7 ]]; then
     export DIB_DHCP_NETWORK_MANAGER_AUTO=${DIB_DHCP_NETWORK_MANAGER_AUTO:-true}
 fi
 
+# note(JayF): Recent downstream security updates for CentOS Stream8 / RHEL8
+# to python3.6 have broken IPA (specifically, eventlet). On these versions, use
+# a newer python version, but allow an opt-opt for operators who need the old
+# behavior.
+if [[ ${DISTRO_NAME} =~ (centos|rhel) && ${DIB_RELEASE%-stream} == 8 ]]; then
+    export DIB_IPA_USE_PYTHON39=${DIB_IPA_USE_PYTHON39:-true}
+fi
+
 # NOTE(rpittau) force Python version to 3 for debian
 if [[ $DISTRO_NAME =~ debian ]]; then
   DIB_PYTHON_VERSION=3

dib/ironic-python-agent-ramdisk/install.d/ironic-python-agent-ramdisk-source-install/60-ironic-python-agent-ramdisk-install

@@ -15,7 +15,12 @@ UPPER_CONSTRAINTS=/tmp/requirements/upper-constraints.txt
 VENVDIR=/opt/ironic-python-agent
 
 # create the virtual environment using the default python
-python3 -m venv $VENVDIR
+if $DIB_IPA_USE_PYTHON39; then
+  python39 -m venv $VENVDIR
+else
+  python3 -m venv $VENVDIR
+fi
+
 REQUIRED_PIP_STR="21.3.1"
 REQUIRED_PIP_TUPLE="(21, 3, 1)"
 

dib/ironic-python-agent-ramdisk/package-installs.yaml

@@ -37,6 +37,11 @@ libssl-dev:
 python-dev:
     build-only: true
 
+python39:
+  when: DIB_IPA_USE_PYTHON39 = true
+python39-devel:
+  when: DIB_IPA_USE_PYTHON39 = true
+
 # The base minimum element uninstalls firmware, but it's needed for bare metal.
 linux-firmware:
   phase: post-install.d