Optimize the error message of gitlab-url again

What does this MR do and why?

Related issue: https://jihulab.com/gitlab-cn/gitlab/-/issues/3683

当前 MR 是之前 MR !32 (merged) 的补充：

• 补充单元测试，覆盖各种 http 网络请求的错误
• 兜底所有网络错误（之前只兜底了一部分），避免请求 Gitlab Pipeline API 时打印错误栈信息

Screenshots or screen recordings

Before	After

How to set up and validate locally

略。