I think the reason you're seeing this (and it then disappearing in Sean's
case) is likely that there was a change in another that required a
recompile of a module dependency.
Maven doesn't do this automatically by default. So it eventually goes away
when you do a full build either with Maven or SBT
I think one thing that is contributing to this a lot too is the general
issue of the tests taking up a lot of file descriptors (10k+ if I run them
on a standard Debian machine).
There are a few suits that contribute to this in particular like
`org.apache.spark.ExecutorAllocationManagerSuite` which,
