PostgreSQL 10 changes in exclusion constraints - did something change?

Did something change with how exclusion constraints are handled? I'm trying
to troubleshoot a regression we are having with PostGIS raster support.

As best I can guess, it's because exclusion constraints that used to work in
past versions are failing in PostgreSQL 10 with an error something like
this:

ERROR: conflicting key value violates exclusion constraint
"enforce_spatially_unique_test_raster_columns_rast"
ERROR: new row for relation "test_raster_columns" violates check constraint
"enforce_coverage_tile_rast"

Unfortunately I don't know how long this has been an issue since we had an
earlier test failing preventing the raster ones from being tested.

Thanks,
Regina