It's a vim undo file. I should probably close this PR as it's far too huge 
currently anyway :-)


On 15 February 2014 00:48:55 David Reid <notifications@github.com> wrote:

> > @@ -1,3 +1,4 @@
> > +*.un~
>
> What is a `.un~`?
>
> If nothing in our development infrastructure produces one, maybe you want 
> to add it to your global ignore file?
>
> https://help.github.com/articles/ignoring-files#global-gitignore
>
>
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/pyca/cryptography/pull/463/files#r9769784