explicit error message when reading configuration fails

bin/access-check-manager.pl.in

@@ -49,6 +49,9 @@ pod2usage(
 my $configuration_file =
     $options{configuration} || '@confdir@/manager.conf';
 my $configuration = Config::Tiny->read($configuration_file);
+if (!$configuration) {
+    die Config::Tiny->errstr() . "\n";
+}
 
 AccountManager::DB->register_db(
     driver   => $configuration->{database}->{type},