Previously, if an exception was raised from an event listener, and the
`-P` option was specified, the debugger would be started not for the
original error but for the `ExtensionError` wrapping it that was
raised by `EventManager.emit`. That made it difficult to debug the
error.
With this change, when `-P` is specified, wrapping of errors in
`ExtensionError` is disabled, which allows pdb to debug the original
error.