Fix fileExists check

Change-Id: I04326b4d5427039c823f4f4cd5bcf0b758ae2fc1
diff --git a/src/com/mirantis/mk/Python.groovy b/src/com/mirantis/mk/Python.groovy
index 576d5d4..08da637 100644
--- a/src/com/mirantis/mk/Python.groovy
+++ b/src/com/mirantis/mk/Python.groovy
@@ -265,7 +265,7 @@
     def common = new com.mirantis.mk.Common()
     configFile = "default_config.yaml"
     writeFile file: configFile, text: context
-    if (fileExists(templatePath + 'tox.ini')) {
+    if (fileExists(new File(templatePath, 'tox.ini').toString())) {
         withEnv(["CONFIG_FILE=$configFile",
                  "OUTPUT_DIR=$outputDir",
                  "TEMPLATE=$template"