Adding the following to Xyz should do the trick.

$src_pkg = 'Xyz';
$src_pkg =~ s{::}{/}g;
$src_pkg .= '.pm';
$dst_pkg = 'Xyz::XML';
$dst_pkg =~ s{::}{/}g;
$dst_pkg .= '.pm';
$INC{$dst_pkg} = $INC{$src_pkg};
[download]

It tells Perl that Xyz::XML is already loaded, so Perl will be happy to tell Class::Trait it was successfully loaded when Class::Traits tries to load it.