Wrap exception in debugger if not in tty

def _exception(etype, eval_, etrace):
        """ Wrap exception in debugger if not in tty """
        if hasattr(sys, 'ps1') or not sys.stderr.isatty():
            # we are in interactive mode or we don't have a tty-like
            # device, so we call the default hook
            sys.__excepthook__(etype, eval_, etrace)
        else:
            # we are NOT in interactive mode, print the exception...
            traceback.print_exception(etype, eval_, etrace, limit=2,
                                      file=sys.stdout)
            six.print_()
            # ...then start the debugger in post-mortem mode.
            pdb.pm()