Ability to switch Salt lib to work with Python 3 has been added

Related-Prod: PRODX-19911
Change-Id: Ief26d607085d78e895e51e9e2bbbc1887f469c35
diff --git a/src/com/mirantis/mk/Python.groovy b/src/com/mirantis/mk/Python.groovy
index 9c9bf88..e8d7ea5 100644
--- a/src/com/mirantis/mk/Python.groovy
+++ b/src/com/mirantis/mk/Python.groovy
@@ -484,13 +484,13 @@
  * @param url SALT_MASTER_URL
  * @param credentialsId Credentials to salt api
  */
-def setupPepperVirtualenv(path, url, credentialsId) {
+def setupPepperVirtualenv(path, url, credentialsId, python_version = 'python2') {
     def common = new com.mirantis.mk.Common()
 
     // virtualenv setup
     // pin pepper till https://mirantis.jira.com/browse/PROD-18188 is fixed
     requirements = ['salt-pepper>=0.5.2,<0.5.4']
-    setupVirtualenv(path, 'python2', requirements, null, true, true)
+    setupVirtualenv(path, python_version, requirements, null, true, true)
 
     // pepperrc creation
     rcFile = "${path}/pepperrc"