def clean_channel_worker_username(self):
channel_worker_username = self.cleaned_data['<STR_LIT>'].strip()<EOL>try:<EOL><INDENT>User.objects.get(username=channel_worker_username)<EOL><DEDENT>except User.DoesNotExist:<EOL><INDENT>raise ValidationError(<EOL>ValidationMessages.INVALID_CHANNEL_WORKER.format(<EOL>channel_worker_username=channel_worker_username<EOL>)<EOL>)<EOL><DEDENT>return channel_worker_username<EOL>
Clean enterprise channel worker user form field

Returns:
    str: the cleaned value of channel user username for transmitting courses metadata.