Update internals.py

Author: mroeschke

pandas/core/internals.py

@@ -373,7 +373,7 @@ def fillna(self, value, limit=None, inplace=False, downcast=None,
         mask = isnull(self.values)
         if limit is not None:
             if is_integer(limit) and limit < 1:
-                raise ValueError('Limit must be greater than 0.')
+                raise ValueError('Limit must be non-negative.')
             if self.ndim > 2:
                 raise NotImplementedError("number of dimensions for 'fillna' "
                                           "is currently limited to 2")