So if we're going to change the error messages, it would be nice if the 
new error messages were grammatical English.  'complex division by zero' 
is fine, but e.g.  'float modulo by zero' doesn't really make sense.

Actually I'd be fine with 'float division by zero' for this, since there's 
an implicit division involved in computing a remainder.  Or perhaps 
something more verbose, like 'right-hand argument to modulo operation is 
zero'.