RestrictedPython information leakage via `AttributeError.obj` and the `string` module

RestrictedPython is a restricted execution environment for Python to run untrusted code. A user can gain access to protected (and potentially sensible) information indirectly via AttributeError.obj and the string module. The problem will be fixed in version 7.3. As a workaround, If the application does not require access to the module string, it can remove it from RestrictedPython.Utilities.utility_builtins or otherwise do not make it available in the restricted execution environment.