drop python2.7 from generate-constraints

Change-Id: I5e51b46afbc26332368525f61a84ff9bd0536a1e

playbooks/proposal/propose_update.sh

@@ -37,9 +37,8 @@ elif [ "$OWN_PROJECT" == "requirements-constraints" ] ; then
     virtualenv $VENV
     $VENV/bin/pip install -e .
     function update {
-        $VENV/bin/generate-constraints -b blacklist.txt -p /usr/bin/python2.7 \
-            -p /usr/bin/python3.6 -r global-requirements.txt \
-            --version-map 3.6:3.7 --version-map 3.6:3.8 \
+        $VENV/bin/generate-constraints -b blacklist.txt -p /usr/bin/python3.6 \
+            -p /usr/bin/python3.8 -r global-requirements.txt \
             > $1/upper-constraints.txt
     }
 elif [ "$OWN_PROJECT" == "devstack-plugins-list" ] ; then