In the case of extending Exception, the raised error is around the
configuration of the constructors. However, there is no valid
configuration of constructors to be found, and therefore, the better
user facing message is to say that the class cannot be extended as
written.
Change-Id: I5950d438877c450c44cdc914f9f20d7779a64768
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/154126
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Mike Fairhurst
e0164ec47e