Only build debconf if it exists

Not all branches have a debconf directory, so only build the guide if
the directory exists.

Change-Id: I3dda9da6f78b54a7f821562a04c1ba2d20823312

bin/doc-tools-check-languages

@@ -121,20 +121,23 @@ function build_rst {
 
         for tag in $INSTALL_TAGS; do
             if [[ "$tag" == "debconf" ]]; then
-                # Build the guide with debconf
-                # To use debian only contents, use "debian" tag.
-                BUILD_DIR="${DOC_DIR}${book}-${tag}/build-${tag}/html"
-                DOCTREES="${BUILD_DIR}.doctrees"
-                tox -evenv -- sphinx-build -q -E -t debian \
-                    -D language=${language} \
-                    -d ${DOCTREES} \
-                    ${DOC_DIR}${book}-${tag}/source/ \
-                    ${BUILD_DIR}
-                PUBLISH_DIR=publish-docs/${language}/${book}-${tag}
-                mkdir -p ${PUBLISH_DIR}
-                rsync -a ${DOC_DIR}${book}-${tag}/build-${tag}/html/ \
-                    ${PUBLISH_DIR}
-                echo $MARKER_TEXT > ${PUBLISH_DIR}/.root-marker
+                # Not all branches have this directory
+                if [[ -d ${DOC_DIR}${book}-${tag}/source ]] ; then
+                    # Build the guide with debconf
+                    # To use debian only contents, use "debian" tag.
+                    BUILD_DIR="${DOC_DIR}${book}-${tag}/build-${tag}/html"
+                    DOCTREES="${BUILD_DIR}.doctrees"
+                    tox -evenv -- sphinx-build -q -E -t debian \
+                        -D language=${language} \
+                        -d ${DOCTREES} \
+                        ${DOC_DIR}${book}-${tag}/source/ \
+                        ${BUILD_DIR}
+                    PUBLISH_DIR=publish-docs/${language}/${book}-${tag}
+                    mkdir -p ${PUBLISH_DIR}
+                    rsync -a ${DOC_DIR}${book}-${tag}/build-${tag}/html/ \
+                        ${PUBLISH_DIR}
+                    echo $MARKER_TEXT > ${PUBLISH_DIR}/.root-marker
+                fi
             else
                 ##
                 # Because Sphinx uses the first heading as title regardless of