fix type of exception

nifty/field.py

@@ -451,7 +451,7 @@ class Field(object):
             tval = getattr(self.val, op)(other)
             return self if tval is self.val else Field(self.domain, tval)
 
-        raise NotImplementedError
+        raise TypeError
 
     def __add__(self, other):
         return self._binary_helper(other, op='__add__')

nifty/operators/linear_operator.py

@@ -102,7 +102,7 @@ class LinearOperator(with_metaclass(
             return DiagonalOperator(thing)
         if np.isscalar(thing):
             return ScalingOperator(thing, dom)
-        raise NotImplementedError
+        raise TypeError
 
     def __mul__(self, other):
         from .chain_operator import ChainOperator