Trac detected an internal error:
There was an internal error in Trac. It is recommended that you inform your local Trac administrator and give him all the information he needs to reproduce the issue.
To that end, you could create a ticket at this site.
The action that triggered the error was:
(I was just trying to view hg README from Gajim downloads site.)
Steps to reproduce
Section "Mercurial", subsection "Under GNU/Linux", README link.