It turns out you can't use the root user in 5.7 anymore without becoming a sudo'er. That means you can't just run mysql -u root anymore and have to do sudo mysql -u root instead.
That also means that it will no longer work if you're using the root user in a GUI (or supposedly any non-command line application). To make it work you'll have to create a new user with the required privileges and use that instead.
Achei a resposta. Não da mais pra usar root sem sudo, então precisa criar outro usuário com privilégios dentro do database pra conseguir fazer o migrate com sucesso.
CREATE USER 'phpmyadmin'@'localhost' IDENTIFIED BY '';
GRANT ALL PRIVILEGES ON . TO 'phpmyadmin'@'localhost' WITH GRANT OPTION;
FLUSH PRIVILEGES;