fix BYOR config

etc/byor_config.py

@@ -6,4 +6,4 @@
 
 from os.path import join as pjoin
 with open(pjoin(c.JupyterHub.template_paths[0], '_byor_options_form.html')) as form:
-    c.CustomDockerSpawner.options_form = form.read()
+    c.ByorDockerSpawner.options_form = form.read()