您知道如果模块不存在，导入错误消息会是什么样的，所以只需检查一下：

You know what the import error message will look like if the module doesn't exist so just check for that:

try:
    module = module_name + '.tests'
    __import__(module)
except ImportError, e:
    if e.args and e.args[0] == 'No module named ' + module:
        print(module, 'does not exist')
    else:
        print(module, 'failed to import')