diff --git a/firanka/builders.py b/firanka/builders.py
index c309a1df453cbfc21d8797cabd252164bce9328a..dea2b20175bb89b5bf3e31aefe8c622749f8d7aa 100644
--- a/firanka/builders.py
+++ b/firanka/builders.py
@@ -1,5 +1,3 @@
-
-
 import copy
 
 from sortedcontainers import SortedList
diff --git a/firanka/exceptions.py b/firanka/exceptions.py
index 74613976a453cd71bf0000b5815b1c1dc1bed488..a6365b049712d7bb4ceabd8a231f473b18338b8a 100644
--- a/firanka/exceptions.py
+++ b/firanka/exceptions.py
@@ -1,10 +1,4 @@
-
-
-__all__ = [
-    'FirankaError',
-    'NotInDomainError',
-    'DomainError',
-]
+__all__ = ['FirankaError', 'NotInDomainError', 'DomainError']
 
 
 class FirankaError(Exception):
@@ -22,7 +16,8 @@ class NotInDomainError(DomainError):
     Requested index is beyond this domain
     """
 
-    def __init__(self, index, domain):
-        super(NotInDomainError, self).__init__(u'NotInDomainError: %s not in %s' % (index, domain))
+    def __init__(self, index, domain, *args, **kwargs):
+        super().__init__(u'NotInDomainError: %s not in %s' % (index, domain), index, domain,
+                         *args, **kwargs)
         self.index = index
         self.domain = domain
diff --git a/firanka/series/bundle.py b/firanka/series/bundle.py
index ba6c4e4123005374bc6a808b39718cc649debcf2..d73920c8d5fb512720eb52138848913932d7cbeb 100644
--- a/firanka/series/bundle.py
+++ b/firanka/series/bundle.py
@@ -1,5 +1,3 @@
-
-
 import functools
 import logging
 
diff --git a/firanka/series/function.py b/firanka/series/function.py
index c87cff4fbe5ff71d280a671394e2e660e07f0d95..e88e70f2b5651aa8930d9a9e81a33c72c5baa6a2 100644
--- a/firanka/series/function.py
+++ b/firanka/series/function.py
@@ -1,5 +1,3 @@
-
-
 from .base import Series
 
 
diff --git a/firanka/series/modulo.py b/firanka/series/modulo.py
index 9fce0488a0ed53f13b973130df3509f81e463663..28ed2b669011bea01ce3659cf37d2bde1ca39b10 100644
--- a/firanka/series/modulo.py
+++ b/firanka/series/modulo.py
@@ -1,5 +1,3 @@
-
-
 import math
 
 from .base import Series
diff --git a/requirements.txt b/requirements.txt
index 72f6bbc17f3036067e5c55944aa0bebee4b9fc22..4693a5a5f347f037d85017449901e9229dacbf8e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1 @@
-six
 sortedcontainers
diff --git a/setup.py b/setup.py
index 4ad015c8ea43b5de970c0f587c042ab00ca62c49..f9221070f3ea9e1741b611a8fd50b3107179496b 100644
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,3 @@
-# coding=UTF-8
 from setuptools import setup, find_packages
 
 from firanka import __version__
@@ -6,8 +5,8 @@ from firanka import __version__
 setup(
     name='firanka',
     version=__version__,
-    packages=find_packages(exclude=['tests.*', 'tests']),
-    install_requires=open('requirements.txt', 'r').readlines(),
+    packages=find_packages(exclude=['tests.*', 'tests', 'docs']),
+    install_requires=['sortedcontainers'],
     url='https://github.com/smok-serwis/firanka',
     author=u'Piotr Maślanka',
     author_email=u'pmaslanka@smok.co',
diff --git a/tests/test_builder.py b/tests/test_builder.py
index d84e36cc26bbe7bd58a9988fb8004878d891d9f2..f663185a0b825f2ea7411f020c0ac8900de4b1f6 100644
--- a/tests/test_builder.py
+++ b/tests/test_builder.py
@@ -1,6 +1,3 @@
-# coding=UTF-8
-from __future__ import print_function, absolute_import, division
-
 import unittest
 
 from firanka.builders import DiscreteSeriesBuilder
diff --git a/tests/test_intervals.py b/tests/test_intervals.py
index f02bf53cdb47a82f123ef76ab2e7c7d16734fce1..b9abb119a70fdddb1b8aaa6336c3e5167444b062 100644
--- a/tests/test_intervals.py
+++ b/tests/test_intervals.py
@@ -1,6 +1,3 @@
-# coding=UTF-8
-from __future__ import print_function, absolute_import, division
-
 import unittest
 
 from firanka.intervals import Interval
diff --git a/tests/test_series/__init__.py b/tests/test_series/__init__.py
index bb72c1029f6733a83220b9a903502db3df30806f..f5a7fd7b4852a3cca6d9828d7e79a768241d7bc2 100644
--- a/tests/test_series/__init__.py
+++ b/tests/test_series/__init__.py
@@ -1,6 +1,3 @@
-# coding=UTF-8
-from __future__ import print_function, absolute_import, division
-
 import math
 import unittest
 
diff --git a/tests/test_series/common.py b/tests/test_series/common.py
index 062de91ffbe68e6111cb8049f5b888fed179d371..15d3183a7105c4c2db0c5ee4da2ef580929d4b55 100644
--- a/tests/test_series/common.py
+++ b/tests/test_series/common.py
@@ -1,6 +1,3 @@
-# coding=UTF-8
-from __future__ import print_function, absolute_import, division
-
 from firanka.series import FunctionSeries
 
 NOOP = lambda x: x
diff --git a/tests/test_series/test_bundles.py b/tests/test_series/test_bundles.py
index 6692b6676c368e5e9d883ecf54883d97a49249e3..afd701a078f59c22713eb4cbae75c5917a1608da 100644
--- a/tests/test_series/test_bundles.py
+++ b/tests/test_series/test_bundles.py
@@ -1,6 +1,3 @@
-# coding=UTF-8
-from __future__ import print_function, absolute_import, division
-
 import unittest
 
 from firanka.series import DiscreteSeries, FunctionSeries, SeriesBundle, DiscreteSeriesBundle