After testing in 8.3.1 this doesn’t seem to be the case.
The manual states for columnNames A list of alias column names for the returned dataset which isn’t true (it was true for 8.1 at some point). To alleviate future confusion it should note the columnNames length needs to match the paths length.
That being said, I could replicate the error issue if histPath contained a capital letter. If the path is all lowercase, then the columnNames work (note: the returned columnNames will also be lowercase).
@mjadams to test this add .lower() to the histPath. histPath = "histprov:NBU_Main_DB:/sys:NBU_Main:/prov:NBU_Main:/tag:_Gateway/Performance/CPU Usage".lower()