Set python_shell default based on remote execution and __opts__['cmd_safe']

def _python_shell_default(python_shell, __pub_jid):
    '''
    Set python_shell default based on remote execution and __opts__['cmd_safe']
    '''
    try:
        # Default to python_shell=True when run directly from remote execution
        # system. Cross-module calls won't have a jid.
        if __pub_jid and python_shell is None:
            return True
        elif __opts__.get('cmd_safe', True) is False and python_shell is None:
            # Override-switch for python_shell
            return True
    except NameError:
        pass
    return python_shell