From 5dc6da0b20169d71093f81696543ca061847d246 Mon Sep 17 00:00:00 2001
From: Alexandre Duret-Lutz <adl@lrde.epita.fr>
Date: Sat, 4 Jan 2020 17:59:45 +0100
Subject: [PATCH] ipnbdoctest: attempt to restart when the kernel dies

* tests/python/ipnbdoctest.py: Catch kernel deaths, wait a random
number of seconds, and try again up to three times.
---
 tests/python/ipnbdoctest.py | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/tests/python/ipnbdoctest.py b/tests/python/ipnbdoctest.py
index 26918a883..5d7d00d10 100755
--- a/tests/python/ipnbdoctest.py
+++ b/tests/python/ipnbdoctest.py
@@ -18,6 +18,7 @@ import time
 import base64
 import re
 import pprint
+import random
 from difflib import unified_diff as diff
 
 from collections import defaultdict
@@ -324,5 +325,20 @@ def test_notebook(ipynb):
 
 if __name__ == '__main__':
     for ipynb in sys.argv[1:]:
-        print("testing %s" % ipynb)
-        test_notebook(ipynb)
+        tries=3
+        while tries:
+            print("testing %s" % ipynb)
+            try:
+                test_notebook(ipynb)
+                break
+            except RuntimeError as e:
+                # If the Kernel dies, try again.  It seems we have spurious
+                # failures when multiple instances of jupyter start in parallel.
+                if 'Kernel died' in str(e):
+                    tries -= 1
+                    if tries:
+                        s = random.randint(1, 5)
+                        print("trying again in", s, "seconds...")
+                        time.sleep(s)
+                else:
+                    raise e