Rewrite /auth-sign-in header.

Author: ryanlovett

jupyter_rsession_proxy/__init__.py

@@ -29,6 +29,18 @@ def get_icon_path():
         os.path.dirname(os.path.abspath(__file__)), 'icons', 'rstudio.svg'
     )
 
+def rewrite_auth(response, request, orig_response, host, port, path):
+    '''
+       As of rstudio-server 1.4ish, it would send the client to /auth-sign-in
+       rather than what the client sees as the full URL followed by
+       /auth-sign-in. See rstudio/rstudio#8888. We rewrite the response by
+       sending the client to the right place.
+    '''
+    for header, v in response.headers.get_all():
+        if header == "Location" and v.startswith("/auth-sign-in"):
+            # Visit the correct page
+            response.headers[header] = request.uri + v
+
 def setup_rserver():
     def _get_env(port):
         return dict(USER=getpass.getuser())
@@ -74,6 +86,7 @@ def _get_cmd(port):
     server_process = {
         'command': _get_cmd,
         'environment': _get_env,
+        'rewrite_response': rewrite_auth,
         'launcher_entry': {
             'title': 'RStudio',
             'icon_path': get_icon_path()