[perl #127167] .^add_method does not work for Role anymore

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# New Ticket Created by  Wenzel Peppmeyer 
# Please include the string:  [perl #127167]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127167 >


role R {}; R.^add_method('foo', method (){})

# OUTPUT«Method 'add_method' not found for invocant of class 
'Perl6::Metamodel::ParametricRoleGroupHOW'␤  in block <unit> at /tmp/ORnhrivIvq 
line 1␤»

# that must have worked until shortly before 6.c because at least one 
# module in the eco system (Crust) depends on it.