start using poetry

.travis.yml

@@ -1,8 +1,10 @@
+---
 language: python
 sudo: false
 cache: pip
 env:
   global:
+    - POETRY_VERSION=1.0.10
     - LD_PRELOAD=/lib/x86_64-linux-gnu/libSegFault.so
     - SEGFAULT_SIGNALS=all
 matrix:
@@ -25,7 +27,7 @@ before_install:
   - uname -a
   - lsb_release -a
 install:
-  - pip install tox
+  - pip install "poetry==${POETRY_VERSION}" tox
   - virtualenv --version
   - easy_install --version
   - pip --version
@@ -38,4 +40,4 @@ after_failure:
 notifications:
   email:
     on_success: never
-    on_failure: never
+    on_failure: never

CONTRIBUTING.rst

@@ -47,19 +47,28 @@ To set up `import-linter` for local development:
 
     git checkout -b name-of-your-bugfix-or-feature
 
-   Now you can make your changes locally.
+    Now you can make your changes locally.
 
-4. When you're done making changes, run all the checks, doc builder and spell checker with `tox <https://tox.readthedocs.io/en/latest/install.html>`_ one command::
+4. Install all development tools like `black`, `mypy` or `flake8` with
+   `poetry <https://python-poetry.org/docs/>`_ by running following command::
+
+    poetry install
+
+    Then you can run each tool like::
+
+    poetry run black src/ tests/
+
+5. When you're done making changes, run all the checks, doc builder and spell checker with `tox <https://tox.readthedocs.io/en/latest/install.html>`_ one command::
 
     tox
 
-5. Commit your changes and push your branch to GitHub::
+6. Commit your changes and push your branch to GitHub::
 
     git add .
     git commit -m "Your detailed description of your changes."
     git push origin name-of-your-bugfix-or-feature
 
-6. Submit a pull request through the GitHub website.
+7. Submit a pull request through the GitHub website.
 
 Pull Request Guidelines
 -----------------------
@@ -87,4 +96,4 @@ To run a subset of tests::
 
 To run all the test environments in *parallel* (you need to ``pip install detox``)::
 
-    detox
+    detox