[Building Sakai] Build & install 2.9 - build question

[Gregory Guthrie]

Why do the install instructions at Confluence (below) say:
    Edit conf/catalina.properties
        Add the following to the line that begins with "common.loader=..."
               ,${catalina.base}/common/classes/,${catalina.base}/common/lib/*.jar

Yet in my fresh install of tomcat  7.0.37 there is no such tomcat/common directory?
Then I get associated error from tomcat on shutdown:
       org.apache.catalina.startup.ClassLoaderFactory validateFile
      WARNING: Problem with directory
           [/usr/share/apache-tomcat-7.0.37/common/classes], exists: [false], isDirectory: [false], canRead: [false]

Is this something to worry about?
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(https://confluence.sakaiproject.org/pages/viewpage.action?pageId=82249316)
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