## errors.SchemaError


A source's new schema cannot be read in the old one, and a node


Usage

``` python
errors.SchemaError()
```


reading it has a contract that was proved against the old one.

Raised by [refresh](Node.refresh.md#sverify.Node.refresh). A source whose data fits its old schema (added columns, widened types) is read in the old schema; otherwise the nodes reading it are planned again and recomputed, which a contracted node cannot be. Build its nodes again on the new schema, so the contract is proved against it. Nothing was applied.