Skip tests for ldapsource with python >= 3.7 Until someone works on fixing these, this should make our CI green again. I tried to use setupModule() to check for python version, but pre_setup_database() is apparently called even when a SkipTest exception is raised there. So handle this in that method.

change_attribute_type('CWCache', 'timestamp', 'TZDatetime')
change_attribute_type('CWUser', 'last_login_time', 'TZDatetime')
change_attribute_type('CWSource', 'latest_retrieval', 'TZDatetime')
drop_attribute('CWSource', 'synchronizing')
add_attribute('CWSource', 'in_synchronization')