Contrary to the 'Affects Versions' tag, this is for the Experimental Snapshots. They aren't listed on the list of versions.

What should be CustomSpawnRules is misspelt as CustomeSpawnRules in the MobSpawnerLogic }}class{{.
Using Yarn mappings names here, not the official names. Apologies, but as a contributor to Yarn I am not allowed to look at the official maps.