The mysql-server package on Ubuntu16.04 was recently updated to disallow
unauthenticated root user login over tcp/ip. This, coupled with pymysql
using tcp/ip whenever host and port is specified causes us to fail to
connect to the database when testing Python3 on Ubuntu16.04.
The fix is to use the unix socket instead.
(cherry picked from commit 748ea39ecd)
This change corrects problems reported by the `yamllint` linter.
Since key duplication problems were removed in 4d48711, this commit
mainly fixes trailing spaces and extra empty lines at beginning/end of
files.
