URL mysql://scott:***@some_host/some_db does not contain a '+drivername'
portion, and will make use of a default driver. A full dbname+drivername://
protocol is recommended. For MySQL, it is strongly recommended that
mysql+pymysql:// be specified for maximum service compatibility.
Change-Id: I8646f135ca2fa28c1858a900bac21acdadb08401
Closes-Bug: #1753342
(cherry picked from commit c9b4316df4)