Bug 1090990: Fix unicode error for emails with non-ascii domains.

This fixes the unicode decode error, but validation will still fail for emails
with non-assci user components (before @). Open question in the bug on what we should
consider valid here based on what ET considers valid.
Testing the validate method by calling a view that uses it seems like a bad idea. You should be testing validate directly, and then ensuring that the view calls `validate_email` properly.