Augmented assignment of object items and slices is not allowed.

## BUG/PROBLEM REPORT / FEATURE REQUEST When I run: ``` a = [1, 2, 3] a[0] += 1 print(a) ``` Error: **Augmented assignment of object items and slices is not allowed.** After my investigation, the issue seems to be in the: _RestrictedPython\transformer.py --> class RestrictingNodeTransformer --> def visit_AugAssign:_ ``` elif isinstance(node.target, ast.Subscript): self.error( node, "Augmented assignment of object items " "and slices is not allowed.") return node ``` I don't understand why operations like **a[0] += 1** have security risks, and RestrictedPython restricts this behavior. I can only bypass the detection by: **a[0] = a[0] + 1**, or by modifying the source code of RestrictedPython. I hope that future versions of RestrictedPython will support this.