During preparing customers DLP environment to the upgrade from DLP 15.0 to 15.5 MP1 URT ends with Index Definition Validation errors: Invalid Non-Primary Key Indexes.
URT returns "Invalid Non-Primary Key Indexes" errors when it is launched on Enforce server with installed additional Language Pack.
Installation of Language Pack creates locale specific indexes in DB which are not included to URT script.
In exampled case issue was caused by installed Czech Language Pack.
These errors does not affect upgrade process and can be completely ignored.
But running of migrator will fail due to these "Invalid Non-Primary Key Indexes" errors as URT script is included into the list of scripts in default configuration of migrator.
To exclude of URT script from default configuration:
After that migrator can be launched.