Add quotes for argument of aptly promotion

Change-Id: I32b3593f5ad9000490573caf8c3c8d7205b4f5da
diff --git a/src/com/mirantis/mk/Aptly.groovy b/src/com/mirantis/mk/Aptly.groovy
index b92efd6..b1b0a2a 100644
--- a/src/com/mirantis/mk/Aptly.groovy
+++ b/src/com/mirantis/mk/Aptly.groovy
@@ -98,7 +98,7 @@
         dumpPublishes(server, timestamp, target)
     }
 
-    sh("aptly-publisher --url ${server} promote --source ${source} --target ${target} --force-overwrite ${opts}")
+    sh("aptly-publisher --url ${server} promote --source '${source}' --target '${target}' --force-overwrite ${opts}")
 
 }