Increase trace/debug information during Ubuntu Docs compile. WWW.Smythies.com

Introduction: Sometimes when working on the Ubuntu Official Documentation it can be virtually impossible to identify the source of some warning or error message.
These notes are a mini how to, mainly as a memory aid for myself.

Procedure:

The trick, when appropriate, is to change the call to xsltproc from within yelp-build to include the --load-trace switch.
Before making any changes, and for restoring later, make a backup copy of yelp-build:

doug@doug-desktop:~/docs-1404/temp-yelp-tools/yelp-tools$ diff /usr/bin/yelp-build.doug /usr/bin/yelp-build.original
396c396
<     ) | (cd "$html_out" && xsltproc --load-trace $html_profile --xinclude \
---
>     ) | (cd "$html_out" && xsltproc $html_profile --xinclude \

A larger context of the area:

        echo '</xsl:for-each>'
        echo '</xsl:template>'
        echo '</xsl:stylesheet>'
    ) | (cd "$html_out" && xsltproc $html_profile --xinclude \
        --stringparam mal.files.copy.icon.dir "$yelp_icon_dir" \
        --stringparam mal.files.copy.js.dir "$yelp_js_dir" \
        - "$html_tmp_infile") | sort | uniq | \
    while read line; do
        use_internal_datadir=`expr substr "$line" 1 1`
        line=`expr substr "$line" 2 1000`

There will be a lot of stuff spewed during compile. Typically, I use a PuTTY SSH session for my terminals, and turn on logging to catch all the spew for post compile investigation. The spew should contain the source file name around the area of the message whose cause we are trying to find.
Here is a bad example (because, in this case, the issue was self created with a test file):

Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/documents-viewgrid.page" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/legal.xml" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/documents.page" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/doug_test.page" ID="(null)"
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Unmatched block element: item
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/files-autorun.page" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/legal.xml" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/files-browse.page" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/legal.xml" ID="(null)"
Loaded URL="file:///home/doug/docs-1404/ubuntu-docs/ubuntu-help/C/files-copy.page" ID="(null)"