FIX #4373 (#4470)

--stats does not work with --dry-run, emit error msg and exit, fixes #4373

src/borg/archiver.py

@@ -4241,6 +4241,9 @@ class Archiver:
         args.progress |= is_serve
         self._setup_implied_logging(vars(args))
         self._setup_topic_debugging(args)
+        if getattr(args, 'stats', False) and getattr(args, 'dry_run', False):
+            logger.error("--stats does not work with --dry-run.")
+            return self.exit_code
         if args.show_version:
             logging.getLogger('borg.output.show-version').info('borgbackup version %s' % __version__)
         self.prerun_checks(logger)

src/borg/testsuite/archiver.py

@@ -1870,10 +1870,9 @@ class ArchiverTestCase(ArchiverTestCaseBase):
         self.cmd('init', '--encryption=repokey', self.repository_location)
         self.cmd('create', self.repository_location + '::test1', src_dir)
         self.cmd('create', self.repository_location + '::test2', src_dir)
-        output = self.cmd('prune', '--list', '--stats', '--dry-run', self.repository_location, '--keep-daily=2')
+        output = self.cmd('prune', '--list', '--dry-run', self.repository_location, '--keep-daily=2')
         assert re.search(r'Keeping archive \(rule: daily #1\):\s+test2', output)
         assert re.search(r'Would prune:\s+test1', output)
-        self.assert_in('Deleted data:', output)
         output = self.cmd('list', self.repository_location)
         self.assert_in('test1', output)
         self.assert_in('test2', output)