pythongh-110166: Skip test_gdb on "Unable to locate python frame"

Skip stack trace tests using get_stack_trace() if "Unable to locate
python frame" is logged by gdb.

Author: vstinner

Lib/test/test_gdb/util.py

@@ -269,6 +269,11 @@ def get_stack_trace(self, source=None, script=None,
             # "#1  0x0000000000000000 in ?? ()", the traceback is likely
             # truncated or wrong.
             ' ?? ()',
+
+            # gh-110166: py-bt-full logs "Unable to locate python frame" when
+            # it fails to locate a Python frame. In such case, "bt" may
+            # display "#1  0x0000000000000000 in ?? ()".
+            "Unable to locate python frame",
         ):
             if pattern in out:
                 raise unittest.SkipTest(f"{pattern!r} found in gdb output")