=begin pod

=TITLE class X::Promise::Vowed

=SUBTITLE Error due to directly trying to keep/break a vowed promise.

    class X::Promise::Vowed is Exception { }

This exception is thrown when code tries to keep/break an already vowed
promise without going through the corresponding C<Vow> object.

=head1 Methods

=head2 method promise

    method promise()

Returns the vowed Promise.

=end pod
