Uploading a package with an invalid Project or Icon URL is blocked at verify-upload with no on-screen validation error.

[claycompton]

1. Create a package with an invalid Project URL or Icon URL value. I've verified this with invalid protocols and URLs that exceed 4000 characters.
2. Attempt to upload the package using the Gallery UI.

Result: You'll get as far as the verify-upload page, but once there, there will be a couple obvious problems:
a. There won't be any kind of validation error listing what's wrong with the package, and
b. The "Submit" button, though enabled, will be completely non-functional.

Expected: The experience should parallel that of the nuget.exe command line; you should get an actual error message on upload, ideally presented in the same style as other form validation errors in the site.

[TimLovellSmith]

If > 4000 chars is the only repro scenario then voting straight to 'up for grabs' on this.

[analogrelay]

Why is the validation not appearing though? Can we just get that issue finally fixed?

[analogrelay]

Related to #1682. We need our validation to tell users about problems in their packages.