What is the manifest.xml convention for dependencies of launch files?
Often times packages will build libraries and executables that have certain dependencies, and then related launch files that often pull in more dependencies.
Depending on perspective, the launch file deps could be thought of as non-essential. With that perspective, one might seek to minimize dependencies and leave them out of the manifest.
This is not simply an academic question, since, for example, many python scripts call to roslib.load_manifest which will throw an exception if a package is missing even if it's not strictly necessary.
What is considered to be "best practice" in this situation?