Use rethrow() instead of throw(ex)

Slightly more idiomatic.

Author: JamesWrigley

Diff for: src/sch/Sch.jl

@@ -415,7 +415,7 @@ function cleanup_proc(state, p, log_sink)
             # We allow ProcessExitedException's, which means that the worker
             # shutdown halfway through cleanup.
             if !(ex isa ProcessExitedException)
-                throw(ex)
+                rethrow()
             end
         end
     end