An even better fix might be to make sure that the argument to delay is
treated as int by the options parser in the first place:
--- unattended-upgrade-shutdown.orig 2015-06-15 15:45:43.000000000 +0200
+++ unattended-upgrade-shutdown 2016-09-09 19:23:18.699281993 +0200
@@ -90,7 +90,7 @@
parser.add_option("", "--debug",
action="store_true", dest="debug", default=False,
help="print debug messages")
- parser.add_option("", "--delay", default=10,
+ parser.add_option("", "--delay", default=10, type="int",
help="delay in minutes to wait for unattended-upgrades")
parser.add_option("", "--lock-file",
default="/var/run/unattended-upgrades.lock",
