stop using dict iter* helpers

Change from iter{keys,items,values}() to {keys,items,values}().
Python 3 doesn't offer the iter variants, and we don't really have
any cases where performance is critical where we'd need to avoid
creating the temporary list (which is what Python 2 does).

This is mostly mechanical.

BUG=chromium:980619
TEST=lint is unchanged in chromite
TEST=unittests pass

Change-Id: I591110f2eb5d43bb9268b975b14bd7ade66a4e35
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1689014
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
diff --git a/scripts/cros_fuzz_unittest.py b/scripts/cros_fuzz_unittest.py
index ed1681d..9e83e0a 100644
--- a/scripts/cros_fuzz_unittest.py
+++ b/scripts/cros_fuzz_unittest.py
@@ -288,10 +288,10 @@
   def testUseAndFeaturesNotClobbered(self):
     """Tests that values of certain environment variables are appended to."""
     vars_and_values = {'FEATURES': 'foo', 'USE': 'bar'}
-    for var, value in vars_and_values.iteritems():
+    for var, value in vars_and_values.items():
       os.environ[var] = value
     extra_env = cros_fuzz.GetBuildExtraEnv(cros_fuzz.BuildType.COVERAGE)
-    for var, value in vars_and_values.iteritems():
+    for var, value in vars_and_values.items():
       self.assertIn(value, extra_env[var])
 
   def testCoverageBuild(self):