[perl #132874] writing to utf16 handle gives write_fhb error

# New Ticket Created by  "brian d foy" 
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This little program:

    my $fh = open 'test.txt', :w, :enc('utf16');
    put "filehandle is using {$fh.encoding}";
    $fh.put: 'Some text';

Gives this error:

    filehandle is using utf16
    write_fhb requires a native array of uint8 or int8

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This is Rakudo Star version 2018.01 built on MoarVM version 2018.01
implementing Perl 6.c