Fix comment in test_gdb

Lib/test/test_gdb.py

@@ -63,7 +63,8 @@ gdbpy_version, _ = run_gdb("--eval-command=python import sys; print sys.version_
 if not gdbpy_version:
     raise unittest.SkipTest("gdb not built with embedded python support")
 
-# Verify that "gdb" can load our custom hooks. In theory this should never fail.
+# Verify that "gdb" can load our custom hooks, as OS security settings may
+# disallow this without a customised .gdbinit.
 cmd = ['--args', sys.executable]
 _, gdbpy_errors = run_gdb('--args', sys.executable)
 if "auto-loading has been declined" in gdbpy_errors: