IMAP4Server bodystructure body parameter parenthesized list too deeply parenthesized

New submission from biny <[email protected]>:

The third item in bodystructure is body parameter parenthesized list, RFC 3501 says:

         body parameter parenthesized list
            A parenthesized list of attribute/value pairs [e.g., ("foo"
            "bar" "baz" "rag") where "bar" is the value of "foo", and
            "rag" is the value of "baz"] as defined in [MIME-IMB].

twisted.mail.test.test_imap.NewFetchTestCase.testFetchBodyStructure expects

{{{
[['name', 'thing'], ['key', 'value']]
}}}

and this is clearly wrong.

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Type     : defect
Component: mail
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/3949