[generic] Add a test case for direct links with broken HEAD (#4032)

test/helper.py

@@ -171,3 +171,13 @@ def assertGreaterEqual(self, got, expected, msg=None):
         if msg is None:
             msg = '%r not greater than or equal to %r' % (got, expected)
         self.assertTrue(got >= expected, msg)
+
+
+def expect_warnings(ydl, warnings_re):
+    real_warning = ydl.report_warning
+
+    def _report_warning(w):
+        if not any(re.search(w_re, w) for w_re in warnings_re):
+            real_warning(w)
+
+    ydl.report_warning = _report_warning

test/test_download.py

@@ -8,6 +8,7 @@ sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 
 from test.helper import (
     assertGreaterEqual,
+    expect_warnings,
     get_params,
     gettestcases,
     expect_info_dict,
@@ -100,6 +101,7 @@ def generator(test_case):
             if status['status'] == 'finished':
                 finished_hook_called.add(status['filename'])
         ydl.add_progress_hook(_hook)
+        expect_warnings(ydl, test_case.get('expected_warnings', []))
 
         def get_tc_filename(tc):
             return tc.get('file') or ydl.prepare_filename(tc.get('info_dict', {}))