Code review comment for lp:~sil2100/ubuntu-archive-tools/plus-sign-review

FWIW, the thing that changed was https://code.launchpad.net/~wgrant/launchpad/bug-677270/+merge/279974. Strictly speaking, to match that you ought to use quote(sourcepkg, safe='/~+'), but it makes no difference since there are no longer any characters that are legal in source package names and that are escaped in librarian URLs.