Hi,
Just updated my dev server to the latest version (1.4.0rc1) and my Django server crashed when trying to connect to the local MySQL DB installed on Ubuntu server v16
The error occurs in the code below from django/db/backends/mysql/base.py

def get_new_connection(self, conn_params):
        conn = Database.connect(**conn_params)
        conn.encoders[SafeText] = conn.encoders[six.text_type]
        conn.encoders[SafeBytes] = conn.encoders[bytes]
        return conn

Specifically this line
conn.encoders[SafeBytes] = conn.encoders[bytes]

I've reverted back to 1.13.14 and all is well in the world again, hope this helps
Thanks
Omar