make Violation messages for arguments and answers include the method name

[davidsarah]

For example:

foolscap.tokens.Violation: Violation (<RootSlicer>.<answer-1>): ('cannot serialize <StorageServer ncieuno4> (allmydata.storage.server.StorageServer)',)

does not mention the method name. The linked pull request will change it to:

foolscap.tokens.Violation: Violation (<RootSlicer>.<answer-1-to-getReferenceByName>): ('cannot serialize <StorageServer ncieuno4> (allmydata.storage.server.StorageServer)',)

i.e. mentioning that the answer that failed to serialize was to the method getReferenceByName.

Arguments are handled similarly.

[davidsarah]

​https://github.com/warner/foolscap/pull/12

[Brian Warner]

Huh, I didn't realize that was broken. Method names were meant to be included in the parent slicers (the CallSlicer for the request arguments). I see where AnswerSlicer is missing information.. that part of the patch looks great. Can you confirm that errors in the request arguments don't mention their methodname as part of the parent CallSlicer.describe string? If it's working the way I expected it to, the description should look something like:

<RootSlicer>.<call-REQID-CLID-METHODNAME>.<ARGNUMORNAME>

I'm happy to apply both patches though, even if the extra METHODNAME turns out to be redundant.

[davidsarah]

I missed this question, will look at it when I have time.

[Brian Warner]

Landed in [3aaa370], would still be nice to get specific tests for it eventually.