As you may know, GNU gcc and gdb have not been included in the standard development tools shipped with Apple as part of Xcode and the Command Line Tools for a number of releases, in favor of llvm/clang and lldb.  So test_gdb is typically automatically skipped on current OS X releases.  That said, if you install gcc and gdb from a third-party and build a current Python with it, it would be good if test_gdb passed.  However, the log file you attached hints that gdb may not be functional, at least with the Homebrew Python you appear to be using (built with Clang); note the'Unable to find Mach task port' message.  Can you verify that the gdb you are using does or does not work with the Python in question, perhaps by trying some of the examples in the Developer's Guide (https://docs.python.org/devguide/gdb.html)?