Better error message

theano/tensor/basic.py

@@ -4745,6 +4745,8 @@ class Reshape(Op):
 
     def __init__(self, ndim, name=None):
         self.ndim = ndim
+        if ndim < 0:
+             raise ValueError("The output dimensions after reshape must be 0 or greater")
         assert name is None, 'name attribute for Reshape has been deprecated'
 
     def __str__(self):