upgrade-checklist/Moving from J to Namespace.md at master

TLWebdesign

Class map in J3:

JError::raiseError() should be replaced with native exceptions.
JError::raiseWarning() and JError::raiseNotice should be replaced with calls to application's enqueueMessage() method to display warnings/notices.

This would mean you wrap your code in a try catch block and return the error. Someting like this:

try {
    // Your code here;
} catch (\RuntimeException $e) {
    throw new \Exception($e->getMessage(), 500, $e);
}

Or you would manually report an error back like this:

throw new \Exception(Text::_('Your error message here'), 500);