The support for --diff-filename regressed in RBTools 3.1, due to the

addition of a new review_request_extra_data attribute on

SquashedDiff that wasn't being provided (being a namedtuple, all

arguments always have to be provided). This is now set to the default of

None.
Along with this, the error message shown for a File Not Found contained

the filename but not the revision, making it hard to determine what was

missing. This is now included.

Encountered both of these issues while testing another problem. Verified

that --diff-filename now works, and that the File Not Found error

contained the correct revision.