The first commit makes the postImport callback more consistent (build info is always passed in via the build argument).

The second commit changes the arguments passed to the pre/postRPMSign callback. The callback previously passed unnecessary arguments (attribute, old) and put everything else into the "info" argument. This made it ambiguous as to what the fields in info were referring to. The new arguments are more clear, and provide direct access to all information a callback handler is most likely to be interested in.

It would have been possible to make this an additive-only change by pushing the build information into the info dict. However, this would have retained the unnecessary arguments, and made the ambiguity of the name/version/release fields in the info dict worse. This API change cleans things up, and should be minimally disruptive.