[server] fix unittest_security for py3k
- use source.binary_to_str instead of str(), helps when the backend
returns memoryviews
- fixup str vs bytes
sync_schema_props_perms('cwuri')
helper = repo.system_source.dbhelper
cu = session.cnxset.cu
helper.set_null_allowed(cu, 'moved_entities', 'extid', 'VARCHAR(256)', False)
commit()