As seen on OOPS-983D2075, OOPS-983E2868, OOPS-983H2844, trying to import a branch to LP, to a project which you don't have permission to access the code, causes LP to crash. It should display an error message highlighting the project field, informing the user that he's not allowed to create the branch on that project instead of crashing.
Steps to reproduce:
1) Go to https://code.staging.launchpad.net/+code-imports/+new
2) Select a project you're not allowed to view or touch, ubunet project in the above OOPS case
3) In the "Subversion", "Branch URL" field, insert a svn branch, svn://ratproxy.googlecode.com/svn/trunk/ratproxy-read-only in the above OOPS
4) It should oops like OOPS-984S1141:
BranchCreationForbidden: You cannot create branches for the product u'ubunet'
I know it causes OOPSes, but it's not high priority since it's not something you should be doing anyway.