The output of the "hg diff" command is not very helpful when it comes to binary files; in particular it reports a binary file as having been changed even if it has actually been added.

Because of this, ReviewBoard will check for the existence of the new file in the parent revision, and throw an exception because it can't find it.

This patch disables checking for file existence for binary files altogether in the diffviewer code. I think this makes sense because the diff viewer doesn't show binary file changes anyway, so shouldn't require them to exist.

Created a review request against a Mercurial repo in which a binary file has been added in the parent diff.
Also tried a review request against a changeset which itself adds a binary file.