Improve API error handling

[huanggze]

Signed-off-by: huanggze loganhuang@yunify.com

The current way we handle error drops some info from errorType and error for some scenarios.

Consider a real response example below, we expect the error object carry more info than inconsistent body for response code.

HTTP OK
---
{
    "status":"error",
    "errorType":"internal",
    "error":"multiple matches for labels: many-to-one matching must be explicit (group_left/group_right)"
}

[huanggze]

@beorn7

[beorn7]

@bboreham @joe-elliott you might have most context here. Does this make sense?

[joe-elliott]

Without knowing the details of prometheus's API response code it's hard to say definitively, but I do prefer the changes @huanggze has made to the existing code.

With these changes the error is only hardcoded to "inconsistent body for response code" if the body says "success" but the http status is error. Otherwise you always get the error as returned from prometheus which I like.

[beorn7]

Thanks, everyone. This makes sense to me, too, from my limited understanding. (o: