#simply added this at the end of <cherokee-etc-dir>/site-enabled/default 

Directory /projects {
       Handler fcgi {
          ErrorHandler on
          CheckFile off
          Server localhost:8082 {
                 Env TRAC_ENV_PARENT_DIR "/var/trac"
                 Interpreter "/usr/local/www/cherokee/cgi-bin/trac.fcgi"
          }
       }
}