lint: fix a variety of minor warnings w/newer pylint

BUG=chromium:1006448
TEST=CQ passes

Change-Id: Ie51afcefee7508f252c0341ef3da79a45309d328
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2203762
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/sysmon/system_metrics.py b/scripts/sysmon/system_metrics.py
index f27cfcd..ad6218a 100644
--- a/scripts/sysmon/system_metrics.py
+++ b/scripts/sysmon/system_metrics.py
@@ -152,6 +152,7 @@
 
 def _collect_disk_io_info():
   try:
+    # pylint: disable=dict-items-not-iterating
     disk_counters = psutil.disk_io_counters(perdisk=True).items()
   except RuntimeError as ex:
     if "couldn't find any physical disk" in str(ex):