Allow "raise Exception()"

[antocuni]

This works:

raise Exception
raise Exception("hello")

This doesn't:

raise Exception()

We should probably allow it and make it equivalent to raise Exception("").
We can do it by checking number of arguments in W_Exception.w_NEW:

spy/spy/vm/exc.py

Lines 54 to 72 in ead6d95

	@builtin_method('__new__', color='blue', kind='metafunc')
	@staticmethod
	def w_NEW(vm: 'SPyVM', wam_cls: W_MetaArg, *args_wam: W_MetaArg) -> W_OpSpec:
	# we cannot use the default __new__ because we want to pass w_cls
	w_cls = wam_cls.w_blueval
	assert isinstance(w_cls, W_Type)
	fqn = w_cls.fqn
	T = Annotated[W_Exception, w_cls]
	# the whole "raise Exception(...)" is a bit of a hack at the moment:
	# the C backend can raise only BLUE exceptions, so here we make sure
	# that Exception("...") is blue
	@vm.register_builtin_func(fqn, '__new__', color='blue')
	def w_new(vm: 'SPyVM', w_cls: W_Type, w_message: W_Str) -> T:
	pyclass = w_cls.pyclass
	assert issubclass(pyclass, W_Exception)
	message = vm.unwrap_str(w_message)
	return pyclass(message)
	return W_OpSpec(w_new, [wam_cls] + list(args_wam))

Originally posted by @dpdani in #172 (comment)