Added methods to support "error state" for cron schedule

[luigifab]

Description

This PR allow user to set cron on error without throwing an exception.
Example:

public function testcron($cron = null) {

    $msg = [];
    $objects = Mage::getResourceModel('customer/customer_collection')->setPageSize(5);

    foreach ($objects as $oid => $object) {

        try {
            throw new Exception('test');
            $msg[] = $oid.' OK!';
        }
        catch (Throwable $t) {
            Mage::logException($t);
            $msg[] = $oid.' ERR '.$t->getMessage();
            if (is_object($cron))
                $cron->setIsError(true);
        }
    }

    if (is_object($cron)) {
        $cron->setData('messages', 'memory: '.((int) (memory_get_peak_usage(true) / 1024 / 1024)).
            'M (max: '.ini_get('memory_limit').')'."\n".implode("\n", $msg));
        if (!method_exists($cron, 'getIsError') && ($cron->getIsError() === true)) // without PR 3310
            Mage::throwException('At least one error occurred while...'."\n\n".
                $cron->getData('messages')."\n\n");
    }

    return $msg;
}

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)
• Add yourself to contributors list

[sreichel]

Can we make it mandatory to add return types for new methods? (#2748)

To follow common naming conventions the method should have prefix is or has.

Edit:

Suggestion for naming ... rename field is_error to error_flag. Add 3 methods (setErrorFlag, getErrorFlag and hasErrorFlag)

With #3245 getData could be replaced with getDataByKey ;)

[kyrena]

There is another setIsError/getIsError usage:

magento-lts/app/code/core/Mage/Customer/Helper/Data.php

Line 711 in 3b14b96

$validationMessageEnvelope->setIsError($isError);

magento-lts/app/code/core/Mage/Customer/Model/Observer.php

Line 181 in 3b14b96

if (!$validationMessage->getIsError()) {

[sreichel]

At least a setter method could be added. I'm no fan of magic methods.