Remove pipenv dependency

MANIFEST.in

@@ -3,7 +3,7 @@ include CODE_OF_CONDUCT.md
 include CONTRIBUTING.md
 include *.sh
 include *.rst
-include Pipfile
+include dev-requirements.txt
 include setup.py
 include setup.cfg
 include tox.ini

README.rst

@@ -393,15 +393,14 @@ needed testing requirements for you.  You can specify a particular python versio
 with the ``-e`` flag, e.g. ``tox -e py36``. Static analysis is done with ``tox -e flake8``.
 You can see all available testing environments with ``tox --listenvs``.
 
-If you do not wish to use ``tox``, you can install the testing dependencies and run the
-tests manually using `pytest <https://docs.pytest.org/en/latest/>`_ - ``natsort``
-contains a ``Pipfile`` for use with `pipenv <https://github.com/pypa/pipenv>`_ that
-makes it easy for you to install the testing dependencies:
+If you do not wish to use ``tox``, you can install the testing dependencies with the
+``dev-requirements.txt`` file and then run the tests manually using
+`pytest <https://docs.pytest.org/en/latest/>`_.
 
 .. code-block:: console
 
-    $ pipenv install --skip-lock --dev
-    $ pipenv run python -m pytest
+    $ pip install -r dev-requirements.txt
+    $ python -m pytest
 
 Note that above I invoked ``python -m pytest`` instead of just ``pytest`` - this is because
 `the former puts the CWD on sys.path <https://docs.pytest.org/en/latest/usage.html#calling-pytest-through-python-m-pytest>`_.

dev-requirements.txt

@@ -0,0 +1,9 @@
+coverage
+pytest >= 3.5
+pytest-cov
+pytest-mock >= 1.1
+hypothesis >= 3.8.0
+pytest-faulthandler; platform_python_implementation == 'CPython'
+semver
+# These packages are standard on newer python versions.
+pathlib; python_version < '3.4'

docs/intro.rst

@@ -388,15 +388,14 @@ needed testing requirements for you.  You can specify a particular python versio
 with the ``-e`` flag, e.g. ``tox -e py36``. Static analysis is done with ``tox -e flake8``.
 You can see all available testing environments with ``tox --listenvs``.
 
-If you do not wish to use ``tox``, you can install the testing dependencies and run the
-tests manually using `pytest <https://docs.pytest.org/en/latest/>`_ - ``natsort``
-contains a ``Pipfile`` for use with `pipenv <https://github.com/pypa/pipenv>`_ that
-makes it easy for you to install the testing dependencies:
+If you do not wish to use ``tox``, you can install the testing dependencies with the
+``dev-requirements.txt`` file and then run the tests manually using
+`pytest <https://docs.pytest.org/en/latest/>`_.
 
-.. code-block:: sh
+.. code-block:: console
 
-    $ pipenv install --skip-lock --dev
-    $ pipenv run python -m pytest
+    $ pip install -r dev-requirements.txt
+    $ python -m pytest
 
 Note that above I invoked ``python -m pytest`` instead of just ``pytest`` - this is because
 `the former puts the CWD on sys.path <https://docs.pytest.org/en/latest/usage.html#calling-pytest-through-python-m-pytest>`_.

tox.ini

@@ -18,11 +18,10 @@ skip_missing_interpreters =
 passenv =
     WITH_EXTRAS
 deps =
-    pipenv
+    -r dev-requirements.txt
 extras =
     {env:WITH_EXTRAS:}
 commands =
-    pipenv install --dev --skip-lock
     # Only run How It Works doctest on Python 3.6.
     py36: {envpython} -m doctest -o IGNORE_EXCEPTION_DETAIL docs/howitworks.rst
     # Other doctests are run for all pythons.