Edit(13/08/2017)

Based on @KaraPirinc's comment, in docker version 17 in order to log in (Step 1),

docker login -u username -p password

I also had the same issue.This is how I resolve it.

Step 1: log in to docker hub

docker login --username=<user username> --email=<user email address>

Step2: create a repository in the docker hub. let's say " mysqlserver:sql ".

docker push <user username>/mysqlserver:sql