Format exception handling

[mmattel]

We have example links like this https://<your-owncloud-server>/ that cause an exception when parsing external links.

Unhandled exception:
FormatException: %3Cyour-owncloud-server%3E is not a valid link-local address but contains %. Scope id should be used as part of link-local address. (at character 1)
%3Cyour-owncloud-server%3E

#0      _NativeSocket.escapeLinkLocalAddress (dart:io-patch/socket_patch.dart:5
...

It would be great if just a small message is prined about the case and not the full block and a debug option on the cli to print the full message.