diff --git a/.drone.yml b/.drone.yml
index 471e19a..604e20a 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -1,4 +1,6 @@
+---
 kind: pipeline
+type: docker
 name: default
 
 steps:
diff --git a/.gitignore b/.gitignore
index 84e7f9d..cac950a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -11,3 +11,4 @@ __pycache__
 .mypy_cache
 **/*.egg-info
 **/.eggs
+venv
diff --git a/setup.cfg b/setup.cfg
index 2e08178..36ee50d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -16,7 +16,7 @@ ignore_missing_imports = True
 ignore_missing_imports = True
 
 [tox:tox]
-envlist = py36,py37,py36-lint
+envlist = py{36,37,38},py{36,37,38}-lint
 
 [testenv]
 deps =
@@ -24,13 +24,15 @@ deps =
 commands =
     pytest tests
 
-[testenv:py36-lint]
+[testenv:py{36,37,38}-lint]
 deps =
     black
     flake8
     flake8-black
     mypy
+    isort
 commands =
     black --check --diff setup.py simplex tests
     flake8 simplex tests
-    mypy simplex tests
\ No newline at end of file
+    mypy simplex tests
+    isort -c simplex tests setup.py
diff --git a/setup.py b/setup.py
index 3cf4150..4e1e7a6 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,6 @@ import setuptools
 with open("README.md", "r") as fh:
     long_description = fh.read()
 
-install_requires = []
 test_requires = ["pytest", "mypy", "black", "flake8", "flake8-black"]
 
 setuptools.setup(
@@ -18,7 +17,7 @@ setuptools.setup(
     long_description_content_type="text/markdown",
     url="https://gitea.typename.fr/mikael.capelle/simplex",
     packages=setuptools.find_packages(),
-    install_requires=install_requires,
+    install_requires=[],
     test_requires=test_requires,
     extras_require={"test": test_requires},
     classifiers=[
diff --git a/simplex/__init__.py b/simplex/__init__.py
index 07a8177..9fdac14 100644
--- a/simplex/__init__.py
+++ b/simplex/__init__.py
@@ -1,5 +1,4 @@
 # -*- encoding: utf-8 -*-
 
-# flake8: noqa
 
-from .simplex_dictionary import simplex_dictionary
+from .simplex_dictionary import simplex_dictionary  # noqa: F401
diff --git a/simplex/simplex_dictionary.py b/simplex/simplex_dictionary.py
index 8393879..474c7ad 100644
--- a/simplex/simplex_dictionary.py
+++ b/simplex/simplex_dictionary.py
@@ -1,8 +1,7 @@
 # -*- encoding: utf-8 -*-
 
 import typing
-
-from abc import abstractmethod, ABC
+from abc import ABC, abstractmethod
 from fractions import Fraction
 
 from .magic_dictionary import magic_dictionary
@@ -105,7 +104,8 @@ class simplex_dictionary(typing.Generic[V]):
     @property
     def variables(self) -> typing.List[V]:
         """
-        Returns: The list of variables in this dictionary.
+        Returns:
+            The list of variables in this dictionary.
         """
         return sorted(self.B + self.N)
 
@@ -119,14 +119,16 @@ class simplex_dictionary(typing.Generic[V]):
     @property
     def N(self) -> typing.List[V]:
         """
-        Returns: The list of non-basic variables for this dictionary.
+        Returns:
+            The list of non-basic variables for this dictionary.
         """
         return self.__N
 
     @property
     def a(self) -> magic_dictionary[V, magic_dictionary[V, Fraction]]:
         """
-        Returns: The a matrix of this dictionary.
+        Returns:
+            The a matrix of this dictionary.
         """
         return self._a
 
@@ -236,7 +238,7 @@ class simplex_dictionary(typing.Generic[V]):
         Args:
             name: Name of the dictionary.
         """
-        from IPython.display import display, Math
+        from IPython.display import Math, display
 
         d = (
             r"\begin{{array}}{{r||{}}}".format("r|" * (1 + len(self.B)))
diff --git a/tests/test_magic_dictionary.py b/tests/test_magic_dictionary.py
index 6671867..c0518ff 100644
--- a/tests/test_magic_dictionary.py
+++ b/tests/test_magic_dictionary.py
@@ -4,8 +4,10 @@ from simplex.magic_dictionary import magic_dictionary
 
 
 def test_basic():
-    """Tests that a non-customized magic_dictionary acts
-    as a standard python dictionary."""
+    """
+    Tests that a non-customized magic_dictionary acts
+    as a standard python dictionary.
+    """
 
     d = magic_dictionary()
     assert len(d) == 0
@@ -43,7 +45,9 @@ def test_basic():
 
 
 def test_value_converter():
-    """ Tests that conversion is correctly done. """
+    """
+    Tests that conversion is correctly done.
+    """
 
     # Convert a value to its string representation:
     def converter(x):