def launch_debugger(frame, stream=None):
    """
    Interrupt running process, and provide a python prompt for
    interactive debugging.
    """

    d = {'_frame': frame}  # Allow access to frame object.
    d.update(frame.f_globals)  # Unless shadowed by global
    d.update(frame.f_locals)

    import code, traceback

    i = code.InteractiveConsole(d)
    message = "Signal received : entering python shell.\nTraceback:\n"
    message += ''.join(traceback.format_stack(frame))
    i.interact(message)