Sometimes, bad things happen to your .plist files. Thus, it is prudent to run the following check on your Munki repo before deploying into production:
find {manifests,pkgsinfo} -type f -exec xmllint --output /dev/null {} \;
This will find all the files under the manifests and pkgsifo directories, check them for well-formedness (but not content; you might still have a typo in what you actually want to say!), and report only on the errors.
The output is sent to /dev/null, as xmllint would otherwise spew out all valid plist files to the terminal, effectively hiding any problems you might have had. A --quiet|-q option would have been cleaner...