Use py3.7 for testrail analyzer

Change-Id: Ib479aa949228801d140953af2cd22b6c39533296
diff --git a/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy b/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
index 52c8160..fa5a248 100644
--- a/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
+++ b/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
@@ -281,7 +281,7 @@
                     """)
                     // Install  TestRail reporter to mark known failures test results to TestRail
                     shared.verbose_sh("""\
-                        [ -d /home/jenkins/venv_testrail_analyzer ] || virtualenv --python=python3 /home/jenkins/venv_testrail_analyzer
+                        [ -d /home/jenkins/venv_testrail_analyzer ] || virtualenv --python=python3.7 /home/jenkins/venv_testrail_analyzer
                     """, true, false, true)
                     shared.run_cmd("""\
                         . /home/jenkins/venv_testrail_analyzer/bin/activate; pip install git+https://review.gerrithub.io/ibumarskov/testrail-reporter@b9041b241f3364022cd0ad63510f02aab4352a6b