Generate a new connection file

        Taken from jupyter_client/console_app.py
        Licensed under the BSD license

def _new_connection_file(self):
        """
        Generate a new connection file

        Taken from jupyter_client/console_app.py
        Licensed under the BSD license
        """
        # Check if jupyter_runtime_dir exists (Spyder addition)
        if not osp.isdir(jupyter_runtime_dir()):
            try:
                os.makedirs(jupyter_runtime_dir())
            except (IOError, OSError):
                return None
        cf = ''
        while not cf:
            ident = str(uuid.uuid4()).split('-')[-1]
            cf = os.path.join(jupyter_runtime_dir(), 'kernel-%s.json' % ident)
            cf = cf if not os.path.exists(cf) else ''
        return cf