Yup, /var/log/tomcat6/catalina.out is where I got it.
If that's not it, I am at a loss where to look.
Date: Tue, 18 Feb 2014 17:59:32 +0100
From: thomas.mortagne(a)xwiki.com
To: users(a)xwiki.org
Subject: Re: [xwiki-users] Component manager has not been initialized before lookup
In standard Debian tomcat install I look at
/var/log/tomcat6/catalina.out but might be different in CentOS.