Make devstack run on focal (Ubuntu LTS 20.04)

- Add a nodeset and a platform job
- Drop uwsgi-py2 pkg that no longer exists
- Blacklist tests that are currently failing

Change-Id: Ib4416dc2f5e003fd770f5240a8f78213c56af8e6
diff --git a/stack.sh b/stack.sh
index 80c6d4d..fa27743 100755
--- a/stack.sh
+++ b/stack.sh
@@ -221,7 +221,7 @@
 
 # Warn users who aren't on an explicitly supported distro, but allow them to
 # override check and attempt installation with ``FORCE=yes ./stack``
-if [[ ! ${DISTRO} =~ (bionic|stretch|jessie|f30|f31|opensuse-15.0|opensuse-15.1|opensuse-tumbleweed|rhel8) ]]; then
+if [[ ! ${DISTRO} =~ (bionic|focal|stretch|jessie|f30|f31|opensuse-15.0|opensuse-15.1|opensuse-tumbleweed|rhel8) ]]; then
     echo "WARNING: this script has not been tested on $DISTRO"
     if [[ "$FORCE" != "yes" ]]; then
         die $LINENO "If you wish to run this script anyway run with FORCE=yes"