When I had this same problem with mysql5.6.20 installed with Homebrew, I solved it by going into my.cnf
nano /usr/local/Cellar/mysql/5.6.20_1/my.cnf
Find the line that looks like so:
sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES
Comment above line out and restart mysql server
mysql.server restart
Error gone!