SEBA-282 xosgenx filtering by app or model;
provide a default argument class for XOSProcessor;
remove tabs;
rename unit tests missed by nose2

Change-Id: I07b782982b6733f8828b8a5a72807326f430b1a5
diff --git a/lib/xos-genx/xosgenx/jinja2_extensions/base.py b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
index 3bfcd70..af1c241 100644
--- a/lib/xos-genx/xosgenx/jinja2_extensions/base.py
+++ b/lib/xos-genx/xosgenx/jinja2_extensions/base.py
@@ -164,6 +164,9 @@
 
     # The "id" field is a special field. Every model has one. Put it up front and pretend it's part of the
 
+    if not fields:
+        raise Exception("Model %s has no fields. Check for missing base class." % m["name"])
+
     id_field = {'type': 'int32', 'name': 'id', 'options': {}, "id": "1", "accessor": fields[0]["accessor"]}
 
     fields = [id_field] + fields