Fix validate.py so it works under Python 3.

Author: Kami

.circle/validate.py

@@ -55,4 +55,4 @@ def validate_repo_name(instance, repo_name):
     validate_schema(pack_meta, PACK_SCHEMA)
     pack_ref = validate_pack_contains_valid_ref_or_name(pack_meta)
 
-    print pack_ref
+    print(pack_ref)