Report use statements that use {} with only one entry

components/profile/trace_dump.rs

@@ -5,7 +5,7 @@
 //! A module for writing time profiler traces out to a self contained HTML file.
 
 use profile_traits::time::{ProfilerCategory, TimerMetadata};
-use serde_json::{self};
+use serde_json;
 use std::fs;
 use std::io::Write;