User.php

use TYPO3\Flow\Annotations as Flow;
use Doctrine\ORM\Mapping as ORM;

/**
 * A User
 *
 * @Flow\Entity
 */
class User {

	/**
	 * @var \TYPO3\Flow\Security\Account
	 * @ORM\ManyToOne
	 */
	protected $account;

If someone stumbles upon this issue: It could be solved by deleting the table and re-creating it with utf-8 definition - then a doctrin:update ran through without any further problem.

See: https://twitter.com/brgmn/status/274243407197655040

Since 2.3 Doctrine adds charset/collation information, overriding the default from the DB that was used before. If those do not match, it breaks. Recommended way around this: use migrations, rather than update and make sure the charset data matches (or remove it to use the DB default).

Oh, and always remember: SHOW ENGINE INNODB STATUS is your best friend when you hit error 150…