Package candidates lets you upload a "candidate" giving it a url that others can download from, and gives an opportunity for doc builders and build bots to try the package out. Once the author is satisfied then they can publish to the main package index. This feature is about 95% complete (we think).
What is the other 5%? Related to build-bot/doc-bot integration?
Yes, this ticket is wonderfully vague. Created separate issues: the most important problem before candidates can be used is #72 , after that #71 and #69 ; at that point candidates can be used; less urgent then are issues #70, #68 and #74 (in that order).
See also #3 apparently.