My editors are configured to remove trailing spaces (this is useful for removing artifacts of indentation). The flip side of this is that my patches sometimes contain unrelated trailing spaces fixes.

Trailing spaces are not significant in any CPython source file, their presence I believe mistake. Easier once we remove all spaces and then prevent the appearance of new, than constantly face to unrelated changes. I'm not attaching a patch (it is too big, over 5 MB), anyone can create it by the following commands:

    hg status -cn | tr '\n' '\0' | xargs -0 sed -i -re 's/[ \t]+$//'

It would be good if the Mercurial would had hook, which automatically remove trailing spaces or prohibit to commit patches that contain trailing spaces.