Fix and reenable useless-object-inheritance.

Initial change generated using:
git ls-tree -r HEAD | awk '$1 != "120000" {print $NF}' | \
  grep '\.py$' | grep -v -e ^third_party/ -e '_pb2\.py' | \
  xargs sed -i 's/(object)//g'

Required only a handful of manual edits after that, mostly for
unrelated lint fixes.

BUG=None
TEST=run_tests, CQ

Change-Id: I0c57fdcf20124530ecd33ae3118506a2be9fc0ed
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4637436
Auto-Submit: Alex Klein <saklein@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/scripts/pushimage.py b/scripts/pushimage.py
index 17bc53e..20416e5 100644
--- a/scripts/pushimage.py
+++ b/scripts/pushimage.py
@@ -64,7 +64,7 @@
         )
 
 
-class InputInsns(object):
+class InputInsns:
     """Object to hold settings for a signable board.
 
     Note: The format of the instruction file pushimage outputs (and the signer
@@ -328,9 +328,9 @@
         dest_bucket: Bucket to push results to.
 
     Returns:
-      A dictionary that maps 'channel' -> ['gs://signer_instruction_uri1',
-                                           'gs://signer_instruction_uri2',
-                                           ...]
+        A dictionary that maps 'channel' -> ['gs://signer_instruction_uri1',
+                                            'gs://signer_instruction_uri2',
+                                            ...]
     """
     # Whether we hit an unknown error.  If so, we'll throw an error, but only
     # at the end (so that we still upload as many files as possible).