added error check for partition list

[accelerated]

Based on issue 89

[mfontanini]

Okay only now I checked this PR and the associated issue. What a ridiculous API... The function returns no error but then there can actually be errors? That's completely unexpected.

Anyway, I think this should be alright. My only concern is if this will actually throw for cases where it currently is silently failing (and there's actually not a critical error). Do you know what could cause e.g. assign to throw? Obviously assuming you're using it properly and not assigning some bogus topic name or something like that.

[accelerated]

Hi, yes I agree, if any partitions had an error, the API should have returned an error as well instead of success. The APIs I gave as example are not the only ones that have this behavior (you can grep rdkafka.h file for more but since you're not using all of them it does not matter here), so honestly I'm not sure what type of failures trigger it, maybe assigning invalid partitions, getting metadata for invalid partitions, setting bad offsets that are not within the special offset values, etc. I think that could be a question for librdkafka owner but he seems very busy at the moment.
In my case I wanted to make sure that if I pause/resume before the assignment is made, the pause works and all partitions are actually paused.

[accelerated]

@mfontanini is this ok?

[mfontanini]

Yep, thanks!