Changelog notes do not preserve non-UTF8 characters from original changelog entries

[Robie Basak]

Some old changelog entries contain non-UTF8 characters, such as:

    autoconf2.13 2.13-55
    autogen 1:5.8.3-2
    dbconfig-common 1.8.17
    dpatch 2.0.10
    dput 0.9.2.16ubuntu1
    emacs-goodies-el 24.9-2
    evolution 2.10.1-0ubuntu2
    gmp 2:4.2.2+dfsg-3ubuntu1
    gnome-session 2.17.92-0ubuntu2
    gnupg 1.4.3-2ubuntu1
    iptables 1.3.5.0debian1-1ubuntu1
    jadetex 3.13-2.1ubuntu2
    llvm-toolchain-3.9 1:3.9.1-4ubuntu3~14.04.2

git-ubuntu will soon start to successfully import such changelog entries into changelog notes, but will do so by losing fidelity. The original characters will be lost. This is unfortunate but is due to pygit2 currently not supporting any way to "pass through" the non-unicode code points. We can't for example use "errors=surrogateescape" since pygit2.Repository.create_note() requires a str. I filed https://github.com/libgit2/pygit2/issues/1021 to track this upstream. It's possible to make progress there by writing a patch, but it doesn't seem worth doing that right now for limited benefit in git-ubuntu.

This bug tracks the loss in fidelity in git-ubuntu changelog notes.