chromite: Ensure chromite lints (mostly) clean after pylint uprev

 - remove suppressions for obsolete lint warnings
 - rename suppressions that have been split (arguments-differ)
 - suppress most of the "consider using.." warnings
 - delete unused variables on except: lines
 - fix some obvious things

BUG=b:236161656
TEST=./run_tests

Change-Id: I3a4af178b29687be23215452aa19c10aa83cb52e
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4505565
Tested-by: Trent Apted <tapted@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Trent Apted <tapted@chromium.org>
diff --git a/scripts/loman.py b/scripts/loman.py
index bb0527b..8954939 100644
--- a/scripts/loman.py
+++ b/scripts/loman.py
@@ -6,7 +6,7 @@
 
 import os
 import platform
-import xml.etree.ElementTree as ElementTree
+from xml.etree import ElementTree
 
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib