Rely on packaging dependencies to avoid issues caused by different
package names between Fedora and RHEL (python-PyMySQL vs python2-PyMySQL).
https://review.openstack.org/#/c/245229/4/spec/classes/neutron_db_spec.rb
includes all the discussion that led to this.
Change-Id: Ic8ec00e47b01bc2963018af7accc4a8a1eff8060