Since 72f072f0c PyMySql is the default and preferred python client for MySQL. Drop
The MySQLdb packages was hold for compatibility and fallback.
Drop MySQLdb support due to following reasons:
- MySQLdb does not work with Python 3
- MySQLdb development is no longer maintained and development stopped 6 years ago
- MySQLdb's usage is deprecated for 20 months already
- Python 2 support will be dropped (T213287)
- PyMySQL module is pure python and does not depend on having the mysql client to be installed on the host
- PyMySQL was installed at tool labs already (T189052)
- PyMySQL does not need a MySQL client and installation is much more easier