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/cli/deploy_unittest.py b/cli/deploy_unittest.py
index dceec2d..86c139e 100644
--- a/cli/deploy_unittest.py
+++ b/cli/deploy_unittest.py
@@ -44,7 +44,7 @@
 )
 
 
-class ChromiumOSDeviceFake(object):
+class ChromiumOSDeviceFake:
     """Fake for device."""
 
     def __init__(self):
@@ -80,10 +80,10 @@
         return self.cat_file_output
 
 
-class ChromiumOSDeviceHandlerFake(object):
+class ChromiumOSDeviceHandlerFake:
     """Fake for chromite.lib.remote_access.ChomiumOSDeviceHandler."""
 
-    class RemoteAccessFake(object):
+    class RemoteAccessFake:
         """Fake for chromite.lib.remote_access.RemoteAccess."""
 
         def __init__(self):
@@ -119,7 +119,7 @@
         self._queue.put("advance")
 
 
-class DbApiFake(object):
+class DbApiFake:
     """Fake for Portage dbapi."""
 
     def __init__(self, pkgs):
@@ -140,7 +140,7 @@
         return [pkg_info[key] for key in keys]
 
 
-class PackageScannerFake(object):
+class PackageScannerFake:
     """Fake for PackageScanner."""
 
     def __init__(self, packages, pkgs_attrs, packages_cpvs=None):
@@ -161,7 +161,7 @@
         )
 
 
-class PortageTreeFake(object):
+class PortageTreeFake:
     """Fake for Portage tree."""
 
     def __init__(self, dbapi):