If you run post-review with --diff-only, and there is an error, it is not handled properly.

For example: Remove your post-review cookie, and then try to update an existing review with --diff-only, it will crash with a KeyError (instead of giving you a login prompt).

(Note: looking at this diff does not display the whitespace changes, even if you click "Show Whitespace changes", which makes it a little hard to understand the change.)

Testing done against Perforce (using changesets).

- Posted a new review.
- Updated diff, (new diff displayed as expected).
- Updated diff with cookies removed, (forced login and updated diff as expected).
- Updated diff with --diff-only, (new diff displayed as expected).
- Updated diff with --diff-only with cookies removed, (forced login and updated diff as expected).