This issue was solved with changeset r32410.
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lib/webrick/httpauth/digestauth.rb (_authenticate):
Literal texts in HTTP ABNF is case-insensitive (RFC2616 2.1),
and a ample implementation in RFC2617 also ignores the case
of algorithms. So now this ignores those cases. [ruby-dev:43965] [Feature #4936]
lib/webrick/httpauth/digestauth.rb (initialize):
Because of above, opera_hack is useless and removed.