Do not show a stacktrace if we fail because we got too many args.

The seed command expects only one positional arguments. If we got more
than one, we should exit with a clean error message, instead of crashing
with an uncaught exception and the associated stacktrace.

odk/odk.py

@@ -993,7 +993,7 @@ def seed(config, clean, outdir, templatedir, dependencies, title, user, source,
     mg = Generator()
     if len(repo) > 0:
         if len(repo) > 1:
-            raise Exception('max one repo; current={}'.format(repo))
+            raise click.ClickException('max one repo; current={}'.format(repo))
         repo = repo[0]
     else:
         repo = "noname"