diff --git a/os_apply_config/apply_config.py b/os_apply_config/apply_config.py
index 697c22c..b14e1f8 100644
--- a/os_apply_config/apply_config.py
+++ b/os_apply_config/apply_config.py
@@ -113,7 +113,7 @@ def print_key(
             return
         else:
             raise exc.ConfigException(
-                'key %s does not exist in %s' % (key, config_path))
+                'key {} does not exist in {}'.format(key, config_path))
     value_types.ensure_type(str(config), type_name)
     if isinstance(config, (dict, list, bool)):
         print(json.dumps(config))
@@ -349,8 +349,8 @@ def main(argv=sys.argv):
             opts.metadata = os.environ['OS_CONFIG_FILES'].split(':')
         else:
             opts.metadata = load_list_from_json(opts.os_config_files)
-            if ((not opts.metadata and opts.os_config_files ==
-                 OS_CONFIG_FILES_PATH)):
+            if (not opts.metadata and opts.os_config_files ==
+                    OS_CONFIG_FILES_PATH):
                 logger.warning('DEPRECATED: falling back to %s' %
                                OS_CONFIG_FILES_PATH_OLD)
                 opts.metadata = load_list_from_json(OS_CONFIG_FILES_PATH_OLD)
diff --git a/os_apply_config/collect_config.py b/os_apply_config/collect_config.py
index 35136ba..d58ae0b 100644
--- a/os_apply_config/collect_config.py
+++ b/os_apply_config/collect_config.py
@@ -27,7 +27,7 @@ def read_configs(config_files):
             try:
                 with open(input_path) as input_file:
                     yield (input_file.read(), input_path)
-            except IOError as e:
+            except OSError as e:
                 raise exc.ConfigException('Could not open %s for reading. %s' %
                                           (input_path, e))
 
diff --git a/os_apply_config/oac_file.py b/os_apply_config/oac_file.py
index f341d97..1ea22b7 100644
--- a/os_apply_config/oac_file.py
+++ b/os_apply_config/oac_file.py
@@ -19,7 +19,7 @@ import pwd
 from os_apply_config import config_exception as exc
 
 
-class OacFile(object):
+class OacFile:
     DEFAULTS = {
         'allow_empty': True,
         'mode': None,
@@ -28,7 +28,7 @@ class OacFile(object):
     }
 
     def __init__(self, body, **kwargs):
-        super(OacFile, self).__init__()
+        super().__init__()
         self.body = body
 
         for k, v in self.DEFAULTS.items():
@@ -53,7 +53,7 @@ class OacFile(object):
         for key, default in self.DEFAULTS.items():
             value = getattr(self, key)
             if value != default:
-                a.append("%s=%s" % (key, repr(value)))
+                a.append("{}={}".format(key, repr(value)))
         return ", ".join(a) + ")"
 
     def set(self, key, value):
diff --git a/os_apply_config/renderers.py b/os_apply_config/renderers.py
index 5170870..5d630ac 100644
--- a/os_apply_config/renderers.py
+++ b/os_apply_config/renderers.py
@@ -33,11 +33,11 @@ class JsonRenderer(pystache.Renderer):
             return u
         if escape is None:
             escape = escape_noop
-        return super(JsonRenderer, self).__init__(file_encoding,
-                                                  string_encoding,
-                                                  decode_errors, search_dirs,
-                                                  file_extension, escape,
-                                                  partials, missing_tags)
+        return super().__init__(file_encoding,
+                                string_encoding,
+                                decode_errors, search_dirs,
+                                file_extension, escape,
+                                partials, missing_tags)
 
     def str_coerce(self, val):
         if val is None:
diff --git a/os_apply_config/tests/test_apply_config.py b/os_apply_config/tests/test_apply_config.py
index 5a1c5d7..e4b9110 100644
--- a/os_apply_config/tests/test_apply_config.py
+++ b/os_apply_config/tests/test_apply_config.py
@@ -86,7 +86,7 @@ class TestRunOSConfigApplier(testtools.TestCase):
     """Tests the commandline options."""
 
     def setUp(self):
-        super(TestRunOSConfigApplier, self).setUp()
+        super().setUp()
         self.useFixture(fixtures.NestedTempfile())
         self.stdout = self.useFixture(fixtures.StringStream('stdout')).stream
         self.useFixture(fixtures.MonkeyPatch('sys.stdout', self.stdout))
@@ -234,7 +234,7 @@ class TestRunOSConfigApplier(testtools.TestCase):
 class OSConfigApplierTestCase(testtools.TestCase):
 
     def setUp(self):
-        super(OSConfigApplierTestCase, self).setUp()
+        super().setUp()
         self.logger = self.useFixture(fixtures.FakeLogger('os-apply-config'))
         self.useFixture(fixtures.NestedTempfile())
 
@@ -329,7 +329,7 @@ class OSConfigApplierTestCase(testtools.TestCase):
             apply_config.render_moustache("ab{{x.a}}cd", {"x": {"a": "123"}}))
 
     def test_render_moustache_bad_key(self):
-        self.assertEqual(u'', apply_config.render_moustache("{{badkey}}", {}))
+        self.assertEqual('', apply_config.render_moustache("{{badkey}}", {}))
 
     def test_render_moustache_none(self):
         self.assertEqual('foo: ',
diff --git a/os_apply_config/tests/test_json_renderer.py b/os_apply_config/tests/test_json_renderer.py
index 2b34218..6ebfbdb 100644
--- a/os_apply_config/tests/test_json_renderer.py
+++ b/os_apply_config/tests/test_json_renderer.py
@@ -35,4 +35,4 @@ class JsonRendererTestCase(testtools.TestCase):
         self.assertEqual(desire_structure, result_structure)
         result = x.render('{{a.c}}', context)
         self.addDetail('result', content.text_content(result))
-        self.assertEqual(u'the quick brown fox', result)
+        self.assertEqual('the quick brown fox', result)
diff --git a/os_apply_config/value_types.py b/os_apply_config/value_types.py
index 9f9cb90..7d2595d 100644
--- a/os_apply_config/value_types.py
+++ b/os_apply_config/value_types.py
@@ -39,6 +39,6 @@ def ensure_type(string_value, type_name='default'):
             "requested validation of unknown type: %s" % type_name)
     if not re.match(TYPES[type_name], string_value):
         exception = config_exception.ConfigException
-        raise exception("cannot interpret value '%s' as type %s" % (
+        raise exception("cannot interpret value '{}' as type {}".format(
             string_value, type_name))
     return string_value