Reviews are not migrated to v1 APIs, they still are using v4: https://developers.google.com/my-business/reference/rest/v4/accounts.locations.reviews/list. You have the following problems with your code:

1. Building the service - correct name is mybusiness (no ** around it) and the version is v4. googleapi client has discovery documents in the library but v4 is not there hence the error when it attempts discovery. To fix this you can either download document from https://developers.google.com/static/my-business/samples/mybusiness_google_rest_v4p9.json and save it locally then use build_from_document or you can point discoveryServiceUrl to the link above
2. location_id needs to be in v4 format - accounts/xxxx/location/xxxxx