Code review comment for lp:~abentley/launchpad/forbidden-oops

= Summary =
This fixes bug #492275, "OOPS when submitting merge request for a project that
I don't have access to"

== Proposed fix ==
Catch BranchCreation exceptions and send email to the sender.

== Pre-implementation notes ==
None

== Implementation details ==
The actual exception was using %r, which was causing the name to be shown as
a unicode literal, e.g. u'~person/product'. End users shouldn't see unicode
literals, so I changed it to "%s".

Also, I sorted the imports.

== Tests ==
bin/test test_codehandler -t test_forbidden_target

== Demo and Q/A ==
Use bzr send to request a merge into a project that does not allow you to
create branches in it. If you get back an error, it works. If you get back
nothing or an OOPs, it's broken.

= Launchpad lint =

Checking for conflicts. and issues in doctests and templates.
Running jslint, xmllint, pyflakes, and pylint.
Using normal rules.

Linting changed files:
  lib/lp/code/mail/codehandler.py
  lib/lp/code/mail/tests/test_codehandler.py
  lib/canonical/launchpad/mail/errortemplates/branch-creation-exception.txt
  lib/lp/code/model/branchnamespace.py

== Pylint notices ==

lib/lp/code/mail/codehandler.py
    37: [F0401] Unable to import 'lazr.uri' (No module named uri)

lib/lp/code/model/branchnamespace.py
    20: [F0401] Unable to import 'lazr.lifecycle.event' (No module named lifecycle)