rebased for backport

Certainly not wrong, but the< 0 check for negative error returns seems equally correct to me and is a common C construct.

its not wrong with current python, but the function is documented to return -1 not negative. As this type of error handling is so common its pretty much impossible python could change that but as I fixed one of them that was wrong my OCD forced me to fix all :)

currently numpy is half == -1 and half < 0, we alternatively could change all to < 0, that would make me happy too ;)

OCD is a common trait in programmers. It is a good thing :) I kind of like the< 0, but that may just be familiarity speaking. There are some numpy functions that can return various negative errors, so maybe<0 can be understood asany error and the== -1 as aspecific error.

changed all to < 0

Looks good, thanks Julian.