Finally fix on_error_test hang.

client/tests/on_error_test.py

 #!/usr/bin/env python
 # Copyright 2014 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 import BaseHTTPServer
 import atexit
 import cgi
 import getpass
 import json
@@ skipping 113 matching lines @@
     self.end_headers()
     data = {
       'id': '1234',
       'url': 'https://localhost/error/1234',
     }
     self.wfile.write(json.dumps(data))
 
 
 def start_server():
   """Starts an HTTPS web server and returns the port bound."""
-  # A premade passwordless self-signed certificate. It works because urllib
-  # doesn't verify the certificate validity.
+  # A premade passwordless self-signed certificate. It works because older
+  # urllib doesn't verify the certificate validity. Disable SSL certificate
+  # verification for more recent version.
+  create_unverified_https_context = getattr(
+      ssl, '_create_unverified_context', None)
+  if create_unverified_https_context:
+    ssl._create_default_https_context = create_unverified_https_context
   httpd = HttpsServer(('127.0.0.1', 0), Handler, 'localhost', pem=PEM)
   httpd.start()
   return httpd
 
 
 class OnErrorBase(auto_stub.TestCase):
   HOSTNAME = socket.getfqdn()
 
   def setUp(self):
     super(OnErrorBase, self).setUp()
@@ skipping 270 matching lines @@
   os.environ.pop(on_error._DISABLE_ENVVAR, None)
 
   if len(sys.argv) == 4 and sys.argv[1] == 'run_shell_out':
     sys.exit(run_shell_out(sys.argv[2], sys.argv[3]))
 
   if '-v' in sys.argv:
     unittest.TestCase.maxDiff = None
   logging.basicConfig(
       level=logging.DEBUG if '-v' in sys.argv else logging.ERROR)
   unittest.main()