smoketest: T6510: make verification of migrated configurations mandatory

For every configuration that is tested from smoketest/configs, there must be
a matching smoketest/config-tests file that has all the `set` commands
after the migration.

Example of missing testcases:

  vyos@vyos:~$ /usr/bin/vyos-configtest
  Generating tests
  Loaded migration result test for config "basic-api-service"
  Loaded migration result test for config "basic-vyos"
  Missing migration result test for config "bgp-azure-ipsec-gateway"

  ... aborted

1 files changed, 5 insertions, 4 deletions

diff --git a/smoketest/bin/vyos-configtest b/smoketest/bin/vyos-configtest
index c1b602737..fbf4055ad 100755
--- a/smoketest/bin/vyos-configtest
+++ b/smoketest/bin/vyos-configtest
@@ -55,7 +55,7 @@ def make_test_function(filename, test_path=None):
 
         if test_path:
             config_commands = self.session.show(['configuration', 'commands'])
-            
+
             with open(test_path, 'r') as f:
                 for line in f.readlines():
                     if not line or line.startswith("#"):
@@ -83,9 +83,10 @@ if __name__ == '__main__':
         test_path = os.path.join(config_test_dir, config)
 
         if not os.path.exists(test_path):
-            test_path = None
-        else:
-            log.info(f'Loaded migration result test for config "{config}"')
+            log.error(f'Missing migration result test for config "{config}"')
+            sys.exit(1)
+
+        log.info(f'Loaded migration result test for config "{config}"')
 
         test_func = make_test_function(config, test_path)