using force_bytes for py2 compatibility

Author: crazyeng

wolframclient/language/array.py

@@ -2,7 +2,7 @@
 
 from wolframclient.exception import WolframLanguageException
 from wolframclient.serializers.wxfencoder import constants
-
+from wolframclient.utils.encoding import force_bytes
 import struct
 
 try:
@@ -28,7 +28,7 @@ def _valid_type_or_fail(self, type):
             )
 
     def tobytes(self):
-        return struct.pack(b'<%i%s' % (len(self), bytes(self.struct.format[1], 'ascii')), *self.array)
+        return struct.pack(b'<%i%s' % (len(self), force_bytes(self.struct.format[1])), *self.array)
 
     def __getitem__(self, k):
         return self.array[k]