When installing or upgrading trac on a Debian-like linux machine you might want to use the easy approach of the python setuptools. Trac can be installed or upgraded by using:
Since the release of Subversion 1.5 the version of easy_install included in the Debian repository ran into a compatibility issue. Instead of working as expected it always complained:
error: Unexpected HTML page found at http://svn.edgewall.org/repos/trac/branches/0.11-stable
The problem seems to be that the SVN-Web-Output generated by Subversion 1.5+ is not being understanded by setuptools. In the issue tracker for the trac-plugin-project trac-hacks.org I found the easiest way to solve this problem. You will use the setuptools to update itself and then you won’t have problems anymore:
easy_install -U setuptools
PS: This problem also occured when trying to install plugins from trac-hacks.org since they also use SVN 1.5+.