Restrict access of users to active issues

Hello,

I have a roundup running and I would like to achieve some special
security settings:
- There are two main groups of users: User and SuperUser.
- Each user can only see/edit/append issues/files/messages for whom he
is on the nosy list
- The users in SuperUser group can access all issues
- Any user in the SuperUser group can raise other users to be SuperUser
and lower them to be normal User

The last wish is optional, here the admin could also work manually. This
will not happen too often.

I think this should be possible but I do not see the necessary
information. for example in
http://roundup.sourceforge.net/docs/customizing.html#users-may-only-edit-their-issues
there is a similar setup discussed but this does not involve nosy lists.
I did not succeed in finding the correct python code to check if a
useris was on a given nosy list.

Unfortunately the docs are not too detailed and mention some information
only without explaining. I do not want to work my way though the code as
I am no native python developer and this would take quite much time.

Can you give me a hint?

Thanks a lot
Christian

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