diff --git a/tempest/api/image/v2/test_images.py b/tempest/api/image/v2/test_images.py
index 2e68efd..c846f88 100644
--- a/tempest/api/image/v2/test_images.py
+++ b/tempest/api/image/v2/test_images.py
@@ -119,7 +119,7 @@
 
         # Update Image
         new_image_name = data_utils.rand_name('new-image')
-        body = self.client.update_image(image['id'], [
+        self.client.update_image(image['id'], [
             dict(replace='/name', value=new_image_name)])
 
         # Verifying updating
diff --git a/tempest/api/network/test_extra_dhcp_options.py b/tempest/api/network/test_extra_dhcp_options.py
index dc9042e..ff66e9a 100644
--- a/tempest/api/network/test_extra_dhcp_options.py
+++ b/tempest/api/network/test_extra_dhcp_options.py
@@ -75,7 +75,7 @@
     def test_update_show_port_with_extra_dhcp_options(self):
         # Update port with extra dhcp options
         name = data_utils.rand_name('new-port-name')
-        body = self.ports_client.update_port(
+        self.ports_client.update_port(
             self.port['id'],
             name=name,
             extra_dhcp_opts=self.extra_dhcp_opts)
diff --git a/tempest/api/object_storage/base.py b/tempest/api/object_storage/base.py
index 11273e4..4c49b2a 100644
--- a/tempest/api/object_storage/base.py
+++ b/tempest/api/object_storage/base.py
@@ -71,9 +71,6 @@
     def setup_credentials(cls):
         cls.set_network_resources()
         super(BaseObjectTest, cls).setup_credentials()
-        # credentials may be overwritten by children classes
-        if hasattr(cls, 'os_roles_operator'):
-            cls.os = cls.os_roles_operator
 
     @classmethod
     def setup_clients(cls):
diff --git a/tempest/api/object_storage/test_account_quotas.py b/tempest/api/object_storage/test_account_quotas.py
index 092d369..f46c256 100644
--- a/tempest/api/object_storage/test_account_quotas.py
+++ b/tempest/api/object_storage/test_account_quotas.py
@@ -29,7 +29,6 @@
     @classmethod
     def setup_credentials(cls):
         super(AccountQuotasTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_reselleradmin = cls.os_roles_reseller
 
     @classmethod
diff --git a/tempest/api/object_storage/test_account_quotas_negative.py b/tempest/api/object_storage/test_account_quotas_negative.py
index 60233b4..431bbe9 100644
--- a/tempest/api/object_storage/test_account_quotas_negative.py
+++ b/tempest/api/object_storage/test_account_quotas_negative.py
@@ -29,7 +29,6 @@
     @classmethod
     def setup_credentials(cls):
         super(AccountQuotasNegativeTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_reselleradmin = cls.os_roles_reseller
 
     @classmethod
diff --git a/tempest/api/object_storage/test_account_services.py b/tempest/api/object_storage/test_account_services.py
index 2fb676f..65cebb3 100644
--- a/tempest/api/object_storage/test_account_services.py
+++ b/tempest/api/object_storage/test_account_services.py
@@ -36,7 +36,6 @@
     @classmethod
     def setup_credentials(cls):
         super(AccountTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_operator = cls.os_roles_operator_alt
 
     @classmethod
diff --git a/tempest/api/object_storage/test_account_services_negative.py b/tempest/api/object_storage/test_account_services_negative.py
index e98a4f5..3e664d7 100644
--- a/tempest/api/object_storage/test_account_services_negative.py
+++ b/tempest/api/object_storage/test_account_services_negative.py
@@ -28,7 +28,6 @@
     @classmethod
     def setup_credentials(cls):
         super(AccountNegativeTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_operator = cls.os_roles_operator_alt
 
     @decorators.attr(type=['negative'])
diff --git a/tempest/api/object_storage/test_container_acl_negative.py b/tempest/api/object_storage/test_container_acl_negative.py
index 655626c..e064753 100644
--- a/tempest/api/object_storage/test_container_acl_negative.py
+++ b/tempest/api/object_storage/test_container_acl_negative.py
@@ -29,7 +29,6 @@
     @classmethod
     def setup_credentials(cls):
         super(ObjectACLsNegativeTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_operator = cls.os_roles_operator_alt
 
     @classmethod
diff --git a/tempest/api/object_storage/test_container_sync.py b/tempest/api/object_storage/test_container_sync.py
index 4cb1914..7665b48 100644
--- a/tempest/api/object_storage/test_container_sync.py
+++ b/tempest/api/object_storage/test_container_sync.py
@@ -41,7 +41,6 @@
     @classmethod
     def setup_credentials(cls):
         super(ContainerSyncTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_alt = cls.os_roles_operator_alt
 
     @classmethod
diff --git a/tempest/api/object_storage/test_object_services.py b/tempest/api/object_storage/test_object_services.py
index 556ca2f..d3cdb72 100644
--- a/tempest/api/object_storage/test_object_services.py
+++ b/tempest/api/object_storage/test_object_services.py
@@ -967,7 +967,6 @@
     @classmethod
     def setup_credentials(cls):
         super(PublicObjectTest, cls).setup_credentials()
-        cls.os = cls.os_roles_operator
         cls.os_alt = cls.os_roles_operator_alt
 
     @classmethod
diff --git a/tempest/api/object_storage/test_object_temp_url.py b/tempest/api/object_storage/test_object_temp_url.py
index 91bc677..217dead 100644
--- a/tempest/api/object_storage/test_object_temp_url.py
+++ b/tempest/api/object_storage/test_object_temp_url.py
@@ -103,7 +103,7 @@
         self.assertEqual(body, self.content)
 
         # Testing a HEAD on this Temp URL
-        resp, body = self.object_client.head(url)
+        resp, _ = self.object_client.head(url)
         self.assertHeaders(resp, 'Object', 'HEAD')
 
     @decorators.idempotent_id('671f9583-86bd-4128-a034-be282a68c5d8')
@@ -142,11 +142,11 @@
                                  expires, self.key)
 
         # trying to put random data in the object using temp url
-        resp, body = self.object_client.put(url, new_data, None)
+        resp, _ = self.object_client.put(url, new_data, None)
         self.assertHeaders(resp, 'Object', 'PUT')
 
         # Testing a HEAD on this Temp URL
-        resp, body = self.object_client.head(url)
+        resp, _ = self.object_client.head(url)
         self.assertHeaders(resp, 'Object', 'HEAD')
 
         # Validate that the content of the object has been modified
diff --git a/tempest/api/object_storage/test_object_version.py b/tempest/api/object_storage/test_object_version.py
index dc0d179..4799053 100644
--- a/tempest/api/object_storage/test_object_version.py
+++ b/tempest/api/object_storage/test_object_version.py
@@ -51,7 +51,7 @@
     def test_versioned_container(self):
         # create container
         vers_container_name = data_utils.rand_name(name='TestVersionContainer')
-        resp, body = self.container_client.create_container(
+        resp, _ = self.container_client.create_container(
             vers_container_name)
         self.containers.append(vers_container_name)
         self.assertHeaders(resp, 'Container', 'PUT')
@@ -59,7 +59,7 @@
 
         base_container_name = data_utils.rand_name(name='TestBaseContainer')
         headers = {'X-versions-Location': vers_container_name}
-        resp, body = self.container_client.create_container(
+        resp, _ = self.container_client.create_container(
             base_container_name,
             metadata=headers,
             metadata_prefix='')
@@ -76,20 +76,20 @@
         data_2 = data_utils.random_bytes()
         resp, _ = self.object_client.create_object(base_container_name,
                                                    object_name, data_2)
-        resp, body = self.object_client.get_object(base_container_name,
-                                                   object_name)
+        _, body = self.object_client.get_object(base_container_name,
+                                                object_name)
         self.assertEqual(body, data_2)
         # delete object version 2
         resp, _ = self.object_client.delete_object(base_container_name,
                                                    object_name)
         self.assertContainer(base_container_name, '1', '1024',
                              vers_container_name)
-        resp, body = self.object_client.get_object(base_container_name,
-                                                   object_name)
+        _, body = self.object_client.get_object(base_container_name,
+                                                object_name)
         self.assertEqual(body, data_1)
         # delete object version 1
-        resp, _ = self.object_client.delete_object(base_container_name,
-                                                   object_name)
+        self.object_client.delete_object(base_container_name,
+                                         object_name)
         # containers should be empty
         self.assertContainer(base_container_name, '0', '0',
                              vers_container_name)