Just upgraded successfully to Magento 2.1.2 through composer:
composer require magento/product-community-edition 2.1.2 --no-update
composer update
rm -rf var/di var/generation var/view_preprocessed var/cache var/page_cache
chown -R user:group .
chmod u+x bin/magento
php bin/magento cache:flush
php bin/magento setup:upgrade
php bin/magento setup:static-content:deploy
php bin/magento indexer:reindex