Simplify formatting of XML and XSD files (#114)

Also fixes a bug where a *.tmp file was committed by Travis CI if a parsing error was encountered during linting

.travis/xmllint-check.sh

@@ -1,4 +1,23 @@
 #!/bin/bash
-/usr/bin/find . -type f \( -name "*.xsd" -or -name "*.xml" \) -print0 | while read -r -d $'\0' filename; do XMLLINT_INDENT=$'\t' xmllint --encode UTF-8 --pretty 1 "${filename}" > "${filename}.pretty"; mv "${filename}.pretty" "${filename}"; grep -i -v "xmlspy" "${filename}" > "${filename}.tmp" && mv "${filename}.tmp" "${filename}"; done;
-echo "finished formatting"
+# The -e flag causes the script to exit as soon as one command returns a non-zero exit code
+set -e
+
+echo "Formatting XSD and XML files"
+
+PARSING_ERROR=0
+while IFS= read -r -d $'\0' filename; do
+  if XMLLINT_INDENT=$'\t' xmllint --encode UTF-8 --pretty 1 "${filename}" >"${filename}.pretty"; then
+    grep -i -v "xmlspy" "${filename}.pretty" >"${filename}"
+  else
+    PARSING_ERROR=$?
+    echo -e "\033[0;31mParsing of file '${filename}' failed\033[0m"
+  fi
+  rm "${filename}.pretty"
+done < <(/usr/bin/find . -type f \( -name "*.xsd" -or -name "*.xml" \) -print0)
+
+if [ ${PARSING_ERROR} -ne 0 ]; then
+  exit ${PARSING_ERROR}
+fi
+echo -e '\033[0;32mFinished formatting XSD and XML files\033[0m'
+
 # xmllint --noout --schema OJP.xsd examples/subdirectory1/*xml examples/subdirectory2/*xml