EHN: Add linting instruction in CONTRIBUTING.rst

CONTRIBUTING.rst

@@ -2,10 +2,10 @@ Contributing guidelines
 =======================
 
 This page explains how you can contribute to the development of `statsmodels`
-by submitting patches, statistical tests, new models, or examples. 
+by submitting patches, statistical tests, new models, or examples.
 
-`statsmodels` is developed on `Github <https://github.com/statsmodels/statsmodels>`_ 
-using the `Git <http://git-scm.com/>`_ version control system. 
+`statsmodels` is developed on `Github <https://github.com/statsmodels/statsmodels>`_
+using the `Git <http://git-scm.com/>`_ version control system.
 
 Submitting a Bug Report
 ~~~~~~~~~~~~~~~~~~~~~~~
@@ -25,24 +25,35 @@ For a pull request to be accepted, you must meet the below requirements. This gr
 - Each function, class, method, and attribute needs to be documented using docstrings. We conform to the `numpy docstring standard <https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt#docstring-standard>`_.
 - If you are adding new functionality, you need to add it to the documentation by editing (or creating) the appropriate file in ``docs/source``.
 - Make sure your documentation changes parse correctly. Change into the top-level ``docs/`` directory and type::
-  
+
    make clean
    make html
 
-  Check that the build output does not have *any* warnings due to your changes. 
+  Check that the build output does not have *any* warnings due to your changes.
 - Finally, please add your changes to the release notes. Open the ``docs/source/release/versionX.X.rst`` file that has the version number of the next release and add your changes to the appropriate section.
 
+Linting
+~~~~~~~
+
+Due to the way we have the CI builds set up, the linter won't do anything unless the environmental variable $LINT is set to a truthy value.
+
+- On MacOS/Linux
+
+    LINT=true ./lint.sh
+
+- Dependencies: flake8, git
+
 How to Submit a Pull Request
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 So you want to submit a patch to `statsmodels` but aren't too familiar with github? Here are the steps you need to take.
 
 1. `Fork <https://help.github.com/articles/fork-a-repo>`_ the `statsmodels repository <https://github.com/statsmodels/statsmodels>`_ on Github.
-2. `Create a new feature branch <http://git-scm.com/book/en/Git-Branching-Basic-Branching-and-Merging>`_. Each branch must be self-contained, with a single new feature or bugfix. 
+2. `Create a new feature branch <http://git-scm.com/book/en/Git-Branching-Basic-Branching-and-Merging>`_. Each branch must be self-contained, with a single new feature or bugfix.
 3. Make sure the test suite passes. This includes testing on Python 3. The easiest way to do this is to either enable `Travis-CI <https://travis-ci.org/>`_ on your fork, or to make a pull request and check there.
 4. Document your changes by editing the appropriate file in ``docs/source/``. If it is a big, new feature add a note and an example to the latest ``docs/source/release/versionX.X.rst`` file. See older versions for examples. If it's a minor change, it will be included automatically in our relase notes.
 5. Add an example. If it is a big, new feature please submit an example notebook by following `these instructions <https://www.statsmodels.org/devel/dev/examples.html>`_.
-6. `Submit a pull request <https://help.github.com/articles/using-pull-requests>`_ 
+6. `Submit a pull request <https://help.github.com/articles/using-pull-requests>`_
 
 Mailing List
 ~~~~~~~~~~~~
@@ -58,5 +69,5 @@ offers much more detailed information about the process.
 License
 ~~~~~~~
 
-Statsmodels is released under the 
+Statsmodels is released under the
 `Modified (3-clause) BSD license <http://www.opensource.org/licenses/BSD-3-Clause>`_.