Automatic emails not sent after users import from CSV

After importing users from a CSV file, the whole process completes, but when the scheduled cron script tries to send emails to users it returns an error for this partial task:

Notice: Undefined property: stdClass::$auth in xxx/lib/moodlelib.php on line 4731 

Scheduled task failed: Send new user passwords,Authentication plugin {$a} not found. 

We tested different versions and found:
$release = '2.7+ (Build: 20140626)'; - still working
$release = '2.7+ (Build: 20140703)'; - ends with error

The problem is caused by a missing authentication value in the user object, which is required in file moodlelib.php by function update_internal_user_password() on line 4731

$authplugin = get_auth_plugin($user->auth);

Between versions two versions tested there are changes in the function setnew_password_and_mail() and the issue is related to this.

As a hotfix of this issue we changed the function send_new_user_passwords_task function execute(), in the following line:

$newusers = $DB->get_recordset_sql("SELECT u.id as id, u.email,  

...to which we added the new attribute u.auth...

$newusers = $DB->get_recordset_sql("SELECT u.id as id, u.email, u.auth, 

It provides authentication method to following actions and fixes issue.