Better error message in get_vector_length()

theano/tensor/basic.py

@@ -4230,7 +4230,8 @@ def get_vector_length(v):
     """
     v = as_tensor_variable(v)
     if v.ndim != 1:
-        raise TypeError('argument must be symbolic vector')
+        raise TypeError("argument must be symbolic vector, got '%s'" %
+                        v)
     if v.type.broadcastable[0]:
         return 1
     if isinstance(v, gof.Constant) and v.type.ndim == 1: