PROD-36025 Switch venv_testrail_reporter to python3

Change-Id: I98728d4d34a7077d94be1390b5b1f3543fcd1999
diff --git a/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy b/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
index dd866a3..ba52899 100644
--- a/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
+++ b/jobs/pipelines/swarm-bootstrap-salt-cluster-heat.groovy
@@ -265,7 +265,7 @@
                     deleteDir()
                     // Install  TestRail reporter to upload test results to TestRail
                     shared.verbose_sh("""\
-                        [ -d /home/jenkins/venv_testrail_reporter ] || virtualenv /home/jenkins/venv_testrail_reporter
+                        [ -d /home/jenkins/venv_testrail_reporter ] || virtualenv --python=python3.7 /home/jenkins/venv_testrail_reporter
                     """, true, false, true)
                     shared.run_cmd("""\
                         . /home/jenkins/venv_testrail_reporter/bin/activate; pip install git+https://github.com/dis-xcom/testrail_reporter -U