While the upgrade process worked fine on my development system, when I attempted to perform the upgrade on the live database I could only get as far as updating composer.
After this was successfully complete I was unable to do anything else as this is the result of trying to run the CLI tool:
$ php ./bin/magento PHP Fatal error: Uncaught Error: Cannot instantiate interface Magento\Framework\Console\CommandListInterface in .../vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php:73 Stack trace: #0 .../vendor/magento/framework/ObjectManager/ObjectManager.php(57): Magento\Framework\ObjectManager\Factory\Dynamic\Developer->create('Magento\\Framewo...', Array) #1 .../vendor/magento/framework/Console/Cli.php(140): Magento\Framework\ObjectManager\ObjectManager->create('Magento\\Framewo...') #2 .../vendor/magento/framework/Console/Cli.php(112): Magento\Framework\Console\Cli->getApplicationCommands() #3 .../vendor/symfony/console/Symfony/Component/Console/Application.php(91): Magento\Framework\Console\Cli->getDefaultCommands() #4 .../vendor/magento/framework/Console/Cli.php(83): Symfony\Component\Console\Application->__construct('Magento CLI', '2.1.0') #5 /var/www/vho in .../vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php on line 73
The only germane differences I can see is that the failure was in production mode on Amazon Linux AMI release 2016.03, whereas the successful upgrade was in developer mode using OS X. There are no permission issues, and it does not matter if I clear down var and pub/static or restart redis.
Originally Amazon Linux AMI was on PHP 7.0.8, but I downgraded to 7.0.7 after the first answer suggested this as a possible issue. Same error.
I am out of ideas as to why the M2 object manager is failing to instantiate this interface. Any thoughts?