When uploading a new patch, some exceptions aren't caught correctly.
On new review requests, both FileNotFoundException and SCMException will
fall all the way through. When updating a patch on an existing review
request, FileNotFoundException is caught, but SCMException is still a problem.
The expected behavior is a message like what happens with a completely
invalid patch.
A more minor nit: the upload error message looks different between the
'new' and 'update' pages. It would be nice if they were consistent.
