Make practracker produce output in a stable order
It looks like practracker produces different output based on the OS directory traversal order.
Two directories on my macOS machine produce the same file, but with a different line order to the one in git. See the resulting commit here: https://github.com/torproject/tor/pull/837/commits/973451edd1a8f0fe7c07ae5ba7fe8256ef279f95
If we want to automate practracker, we'll need to use a stable sort order for warnings.