Unable to connect to local MySQL db using drush sql-sync
I have faced the same issue.
My solution was to add more rights to mysql user with this comande line :

GRANT ALL PRIVILEGES ON `myDB`.* TO 'mySQLuser'@'localhost' WITH GRANT OPTION


Because previous rights : 

GRANT USAGE ON *.* TO 'mySQLuser'@'localhost' IDENTIFIED BY PASSWORD 'pwd'


Do not seem to be enough.