improved error messages

scalar.py

@@ -21,6 +21,7 @@ def as_scalar(x, name = None):
         return s
     if isinstance(x, Scalar):
         return x
+    raise TypeError("Cannot convert %s to Scalar" % x)
 
 def constant(x):
     res = as_scalar(x)

tensor.py

@@ -316,12 +316,16 @@ def astensor(data, broadcastable=None, name=None):
     if data is None and broadcastable is None:
         raise TypeError("Cannot make a Tensor out of None.")
 
+    _data = data
     data = numpy.asarray(data)
     if broadcastable is None:
         broadcastable = [s==1 for s in data.shape]
     elif broadcastable in [0, 1]:
         broadcastable = [broadcastable] *  len(data.shape)
+    try:
         rval = Tensor(data.dtype, broadcastable, name = name)
+    except TypeError:
+        raise TypeError("Cannot convert %s to Tensor." % _data)
     rval.data = data # will raise if broadcastable was mis-specified
     return rval
 s2t.astensor = astensor