Batch Enrollment - invalid user fails without error message

[pwilkins]

Either a username or an email address may be entered in the Batch Enrollment panel. If a username that is unknown to the system is entered, no email is sent and no warning message is displayed, even though an error message is written to the log.

2015-05-15 12:11:12,173 INFO 5560 [ccx.views] views.py:369 - Invalid user name or email when trying to invite students: pwilkins-stu02

The instructions on the page say, " ... You will not get notification for emails that bounce," but makes no mention of invalid usernames that don't even generate emails. Unless this behavior is consistent with other edX controls, either an error message should be shown or the page instructions should change.