message: Print a backtrace for crates which fail to build
diff: @@ -115,8 +115,11 @@ impl DocBuilder {
  crate::web::metrics::TOTAL_BUILDS.inc();
  }
  error!(
  - "Failed to build package {}-{} from queue: {}",
  - name, version, e
  + "Failed to build package {}-{} from queue: {}\nBacktrace: {}",
  + name,
  + version,
  + e,
  + e.backtrace()
  )
  }
  }
  