I am trying to upgrade V15 to the latest V15 and getting this error 

Traceback (most recent call last):
  File "/cloudclusters/odoo/odoo/service/server.py", line 1260, in preload_registries
    registry = Registry.new(dbname, update_module=update_module)
  File "/cloudclusters/odoo/odoo/modules/registry.py", line 87, in new
    odoo.modules.load_modules(registry, force_demo, status, update_module)
  File "/cloudclusters/odoo/odoo/modules/loading.py", line 484, in load_modules
    modules = Module.search(Module._get_modules_to_load_domain(), order='name')
AttributeError: 'ir.module.module' object has no attribute '_get_modules_to_load_domain'