handle transient 404

tljh/installer.py

@@ -2,6 +2,7 @@ import sys
 import os
 import tljh.systemd as systemd
 import tljh.conda as conda
+from urllib.error import HTTPError
 from urllib.request import urlopen, URLError
 from tljh import user
 import secrets
@@ -151,6 +152,13 @@ def ensure_jupyterhub_running(times=4):
                 continue
             # Everything else should immediately abort
             raise
+        except HTTPError as h:
+            if h.code == 404:
+                # May be transient
+                time.sleep(1)
+                continue
+            # Everything else should immediately abort
+            raise
 
     raise Exception("Installation failed: JupyterHub did not start in {}s".format(times))