Fix exception when set-severity receives invalid logging level

bin/cylc-set-verbosity

@@ -62,7 +62,7 @@ def main(parser, options, suite, severity_str):
     try:
         severity = LOGGING_LVL_OF[severity_str]
     except KeyError:
-        parser.error("Illegal logging level, %s" % severity)
+        parser.error("Illegal logging level, %s" % severity_str)
 
     prompt("Set logging level to %s in %s" % (severity_str, suite),
            options.force)

tests/cli/03-set-verbosity.t

@@ -0,0 +1,25 @@
+#!/bin/bash
+# THIS FILE IS PART OF THE CYLC SUITE ENGINE.
+# Copyright (C) 2008-2019 NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#-------------------------------------------------------------------------------
+# Test "cylc set-verbosity" with a bad verbosity level.
+. "$(dirname "$0")/test_header"
+set_test_number 2
+run_fail "${TEST_NAME_BASE}" cylc set-verbosity duck quack
+contains_ok "${TEST_NAME_BASE}.stderr" <<'__ERR__'
+cylc-set-verbosity: error: Illegal logging level, quack
+__ERR__
+exit