diff --git a/core/_tests/helpers/test_http.py b/core/_tests/helpers/test_http.py
index f9c018d36..e899dcb76 100644
--- a/core/_tests/helpers/test_http.py
+++ b/core/_tests/helpers/test_http.py
@@ -2,8 +2,10 @@ from __future__ import absolute_import
 
 import unittest
 
-from mock import patch
+# pylint: disable=import-error
 from mock import call
+from mock import patch
+# pylint: enable=import-error
 
 from core.helpers.http import HTTPClientZabbix
 
diff --git a/core/_tests/helpers/test_setup_teardown.py b/core/_tests/helpers/test_setup_teardown.py
index cb5d03801..2f1fe744b 100644
--- a/core/_tests/helpers/test_setup_teardown.py
+++ b/core/_tests/helpers/test_setup_teardown.py
@@ -3,8 +3,10 @@ from __future__ import print_function
 
 import unittest
 
+# pylint: disable=import-error
 from mock import call
 from mock import patch
+# pylint: enable=import-error
 
 from core.helpers import setup_teardown
 
@@ -159,6 +161,11 @@ class TestWrappers(unittest.TestCase):
             'cls was not filtered from @classmethod!'
         )
 
+        # Allow to replace function by None in special cases
+        self.assertIsNone(
+            call_in_context(None, {'test_arg': 'test_val'})
+        )
+
 
 @patch('core.helpers.setup_teardown.__getcallargs', return_value={'arg': True})
 @patch('core.helpers.setup_teardown.__call_in_context')
@@ -166,12 +173,6 @@ class TestSetupTeardown(unittest.TestCase):
     def test_basic(self, call_in, getargs):
         arg = True
 
-        def setup_func():
-            pass
-
-        def teardown_func():
-            pass
-
         @setup_teardown.setup_teardown()
         def positive_example(arg):
             return arg
diff --git a/core/_tests/models/test_collector_client.py b/core/_tests/models/test_collector_client.py
index 14f0c45f9..1d1f20c63 100644
--- a/core/_tests/models/test_collector_client.py
+++ b/core/_tests/models/test_collector_client.py
@@ -3,8 +3,10 @@ from __future__ import unicode_literals
 
 import unittest
 
-from mock import patch
+# pylint: disable=import-error
 from mock import call
+from mock import patch
+# pylint: enable=import-error
 
 from core.models.collector_client import CollectorClient
 
diff --git a/tox.ini b/tox.ini
index 204637b06..a9f39a8f4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -49,7 +49,7 @@ deps=
     {[testenv]deps}
     pylint
 commands=
-    pylint --rcfile=.pylintrc_gerrit fuelweb_test system_test gates_tests fuel_tests run_system_test
+    pylint --rcfile=.pylintrc_gerrit fuelweb_test system_test gates_tests fuel_tests run_system_test core
 
 
 [testenv:pylint-py27-fuelweb]
@@ -91,4 +91,5 @@ deps =
     {[testenv]deps}
 commands =
     py.test --cov-config .coveragerc --cov-report html --cov=core core/_tests
-    coverage report
+    coverage html -d {envlogdir}
+    coverage report --fail-under 75