diff --git a/Lib/test/test_bdb.py b/Lib/test/test_bdb.py
index 70cb096e9..a3abbbb8d 100644
--- a/Lib/test/test_bdb.py
+++ b/Lib/test/test_bdb.py
@@ -59,6 +59,7 @@ from contextlib import contextmanager
 from itertools import islice, repeat
 from test.support import import_helper
 from test.support import os_helper
+from test.support import patch_list
 
 
 class BdbException(Exception): pass
@@ -432,8 +433,9 @@ class TracerRun():
         not_empty = ''
         if self.tracer.set_list:
             not_empty += 'All paired tuples have not been processed, '
-            not_empty += ('the last one was number %d' %
+            not_empty += ('the last one was number %d\n' %
                           self.tracer.expect_set_no)
+            not_empty += repr(self.tracer.set_list)
 
         # Make a BdbNotExpectedError a unittest failure.
         if type_ is not None and issubclass(BdbNotExpectedError, type_):
@@ -728,6 +730,14 @@ class StateTestCase(BaseTestCase):
     def test_skip(self):
         # Check that tracing is skipped over the import statement in
         # 'tfunc_import()'.
+
+        # Remove all but the standard importers.
+        sys.meta_path[:] = (
+            item
+            for item in sys.meta_path
+            if item.__module__.startswith('_frozen_importlib')
+        )
+
         code = """
             def main():
                 lno = 3
@@ -1224,5 +1234,12 @@ class IssuesTestCase(BaseTestCase):
                 tracer.runcall(tfunc_import)
 
 
+class TestRegressions(unittest.TestCase):
+    def test_format_stack_entry_no_lineno(self):
+        # See gh-101517
+        self.assertIn('Warning: lineno is None',
+                      Bdb().format_stack_entry((sys._getframe(), None)))
+
+
 if __name__ == "__main__":
     unittest.main()