testsuite: add test for sched hello failure

Problem: there is no test coverage for a failure of the
sched hello callback.

Add a test that ensures a job whose resources cannot be re-allocated
receives a fatal exception.

t/Makefile.am

@@ -154,6 +154,7 @@ TESTSCRIPTS = \
 	t2280-job-memo.t \
 	t2300-sched-simple.t \
 	t2302-sched-simple-up-down.t \
+	t2303-sched-hello.t \
 	t2310-resource-module.t \
 	t2311-resource-drain.t \
 	t2312-resource-exclude.t \

t/t2303-sched-hello.t

@@ -0,0 +1,43 @@
+#!/bin/sh
+
+test_description='test sched hello
+
+Ensure that a job that the scheduler rejects during hello processing
+receives a fatal exception.
+'
+
+# Append --logfile option if FLUX_TESTS_LOGFILE is set in environment:
+test -n "$FLUX_TESTS_LOGFILE" && set -- "$@" --logfile
+. $(dirname $0)/sharness.sh
+
+test_under_flux 1 job
+
+test_expect_success 'start a long-running job' '
+	jobid=$(flux mini submit -n1 -t1h sleep 3600)
+'
+test_expect_success 'unload scheduler' '
+	flux module remove sched-simple
+'
+test_expect_success 'exclude the job node from configuration' '
+	flux config load <<-EOT
+	[resource]
+	exclude = "0"
+	EOT
+'
+test_expect_success 'increase broker stderr log level' '
+	flux setattr log-stderr-level 6
+'
+test_expect_success 'load scheduler' '
+	flux module load sched-simple
+'
+test_expect_success 'job receives exception' '
+	flux job wait-event -t 30 ${jobid} exception
+'
+test_expect_success 'job receives clean event' '
+	flux job wait-event -v -t 30 ${jobid} clean
+'
+test_expect_success 'decrease broker stderr log level' '
+	flux setattr log-stderr-level 5
+'
+
+test_done