URI parse error on Uri containing '?'

[netr0m]

When a request Uri is parsed, and it contains a '?' question mark, it causes an exception:

// Report a parse failure.
  static void _fail(String uri, int index, String message) {    uri: "/lookup_accounts?lowerBoundName=amigos&limit=16"    index: 16    message: "Invalid character"
    throw new FormatException(message, uri, index);
  }

This happens to any Uri containing a '?', although '?' should be allowed (it's a reserved character of Uri's)