Specify Exception for "No UDF found" when the arguments are incorrect

[VictorVerhaert]

When the arguments of e.g. apply_datacube to not match, the error states "No UDF found."
This could be made clearer and more specific to point a user in the right direction of changing the arguments.

Related code:

openeo-python-client/openeo/udf/run_code.py

Lines 147 to 203 in 7ce9292

	def run_udf_code(code: str, data: UdfData) -> UdfData:
	# TODO: current implementation uses first match directly, first check for multiple matches?
	module = load_module_from_string(code)
	functions = ((k, v) for (k, v) in module.items() if callable(v))
	for (fn_name, func) in functions:
	try:
	sig = inspect.signature(func)
	except ValueError:
	continue
	params = sig.parameters
	first_param = next(iter(params.values()), None)
	if (
	fn_name == 'apply_timeseries'
	and 'series' in params and 'context' in params
	and _annotation_is_pandas_series(params["series"].annotation)
	and _annotation_is_pandas_series(sig.return_annotation)
	):
	_log.info("Found timeseries mapping UDF `{n}` {f!r}".format(n=fn_name, f=func))
	return apply_timeseries_generic(data, func)
	elif (
	fn_name in ['apply_hypercube', 'apply_datacube']
	and 'cube' in params and 'context' in params
	and _annotation_is_udf_datacube(params["cube"].annotation)
	and _annotation_is_udf_datacube(sig.return_annotation)
	):
	_log.info("Found datacube mapping UDF `{n}` {f!r}".format(n=fn_name, f=func))
	if len(data.get_datacube_list()) != 1:
	raise ValueError("The provided UDF expects exactly one datacube, but {c} were provided.".format(
	c=len(data.get_datacube_list())
	))
	# TODO: also support calls without user context?
	result_cube = func(cube=data.get_datacube_list()[0], context=data.user_context)
	data.set_datacube_list([result_cube])
	return data
	elif (
	fn_name in ['apply_datacube']
	and 'cube' in params and 'context' in params
	and _annotation_is_data_array(params["cube"].annotation)
	and _annotation_is_data_array(sig.return_annotation)
	):
	_log.info("Found datacube mapping UDF `{n}` {f!r}".format(n=fn_name, f=func))
	if len(data.get_datacube_list()) != 1:
	raise ValueError("The provided UDF expects exactly one datacube, but {c} were provided.".format(
	c=len(data.get_datacube_list())
	))
	# TODO: also support calls without user context?
	result_cube: xarray.DataArray = func(cube=data.get_datacube_list()[0].get_array(), context=data.user_context)
	data.set_datacube_list([XarrayDataCube(result_cube)])
	return data
	elif len(params) == 1 and _annotation_is_udf_data(first_param.annotation):
	_log.info("Found generic UDF `{n}` {f!r}".format(n=fn_name, f=func))
	func(data)
	return data
	raise OpenEoUdfException("No UDF found.")