Use base_url so that the extension works in a JupyterHub setting.

Author: ian-r-rose

jupyterlab_github/__init__.py

@@ -100,5 +100,7 @@ def load_jupyter_server_extension(nb_server_app):
         nb_server_app (NotebookWebApplication): handle to the Notebook webserver instance.
     """
     web_app = nb_server_app.web_app
-    host_pattern = '.*$'
-    web_app.add_handlers(host_pattern, [(r'/github%s' % path_regex, GitHubHandler)])
+    base_url = web_app.settings['base_url']
+    endpoint = url_path_join(base_url, 'github')
+    handlers = [(endpoint + "(.*)", GitHubHandler)]
+    web_app.add_handlers('.*$', handlers)