Add error message for invalid array type

The message is taken from NumericArray itself.

Author: Dorian Birraux

wolframclient/language/array.py

@@ -2,6 +2,7 @@
 
 from wolframclient.serializers.wxfencoder import constants
 from wolframclient.utils.encoding import concatenate_bytes
+from wolframclient.exception import WolframLanguageException
 
 try:
     from collections.abc import Sequence
@@ -15,7 +16,10 @@ def __init__(self, array, type, shape=None):
         self.array = array
         self.shape = shape or (len(array),)
         self.type = type
-        self.struct = constants.STRUCT_MAPPING[type]
+        try:
+            self.struct = constants.STRUCT_MAPPING[type]
+        except KeyError:
+            raise WolframLanguageException('Type %s is not one of the supported array types: %s.' % (type, ', '.join(constants.STRUCT_MAPPING.keys())))
 
     def tobytes(self):
         return concatenate_bytes(self.struct.pack(el) for el in self.array)