D3614: py3: check for None before comparing with integers

[Yuya Nishihara]

> --- a/mercurial/revlog.py
> +++ b/mercurial/revlog.py
> @@ -846,7 +846,7 @@
>      def rawsize(self, rev):
>          """return the length of the uncompressed text for a given revision"""
>          l = self.index[rev][2]
> -        if l >= 0:
> +        if l is not None and l >= 0:

Ugh, rawsize could be None? It smells like a bug.