CI: pin tox version at verify python job

Issue-ID: CIMAN-33
Signed-off-by: Kevin Sandi <ksandi@contractor.linuxfoundation.org>
Change-Id: Ia91281b770dd317c8f387a36e5bdd08fed9362df
diff --git a/jjb/global-templates-python.yaml b/jjb/global-templates-python.yaml
index df37064..dcc5985 100644
--- a/jjb/global-templates-python.yaml
+++ b/jjb/global-templates-python.yaml
@@ -63,7 +63,7 @@
           source ~/lf-env.sh
 
           lf-activate-venv --python python3.8 --venv-file /tmp/.toxenv \
-            tox tox-pyenv virtualenv
+            tox==3.27.1 tox-pyenv virtualenv
 
           if [[ -d /opt/pyenv ]]; then
             echo "---> Setting up pyenv"