Added virtual environment enforcing for pip for the osx installation tutorial

docs/starting/install/osx.rst

@@ -118,7 +118,6 @@ copy your code out of it, and then delete the main directory for the environment
 An useful set of extensions to virtualenv is available in virtualenvwrapper,
 `RTFD <http://virtualenvwrapper.readthedocs.org/en/latest/>`_ to find out more.
 
-
 --------------------------------
 
 This page is a remixed version of `another guide <http://www.stuartellis.eu/articles/python-development-windows/>`_,

docs/starting/pip-virtualenv.rst

@@ -0,0 +1,84 @@
+.. _pip-virtualenv:
+
+Further Configuration of Pip and Virtualenv
+===========================================
+
+Requiring an active virtual environment for ``pip``
+---------------------------------------------------
+
+By now it should be clear that using virtual envirtonments is a great way to keep
+your development environment clean and keeping different projects' requirements
+separate.
+
+When you start working on many different projects, it can be hard to remember to
+activate the related virtual environment when you come back to a specific project.
+As a result of this, it is very easy to install packages globally while thinking
+that you are actually installing the package for the virtual environment of the
+project. Over time this can result in a messy global package list.
+
+In order to make sure that you install packages to your active virtual environment
+when you use ``pip install``, consider adding the following two lines to your
+``~/.bashrc`` file:
+
+.. code-block:: console
+
+    export PIP_REQUIRE_VIRTUALENV=true
+
+After saving this change and sourcing the ``~/.bashrc`` file with ``source ~/.bashrc``,
+pip will no longer let you install packages if you are not in a virtual environment.
+If you try to use ``pip install`` outside of a virtual environment pip will gently
+remind you that an activated virtual environment is needed to install packages.
+
+.. code-block:: console
+
+    $ pip install requests
+    Could not find an activated virtualenv (required).
+
+You can also do this configuration by editing your ``pip.conf`` or ``pip.ini``
+file. ``pip.conf`` is used by Unix and Mac OS X operating systems and it can be
+found at:
+
+.. code-block:: console
+
+    $HOME/.pip/pip.conf
+
+Similarly, the ``pip.ini`` file is used by Windows operating systems and it can
+be found at:
+
+.. code-block:: console
+
+    %HOME%\pip\pip.ini
+
+If you don't have a ``pip.conf`` or ``pip.ini`` file at these locations, you can
+create a new file with the correct name for your operating system.
+
+If you already have a configuration file, just add the following line under the
+``[global]`` settings to require an active virtual environment:
+
+.. code-block:: console
+
+    require-virtualenv = true
+
+If you did not have a configuration file, you will need to create a new one and
+add the following lines to this new file:
+
+.. code-block:: console
+
+    [global]
+    require-virtualenv = true
+
+
+You will of course need to install some packages globally (usually ones that you
+use across different projects consistenly) and this can be accomplished by adding
+the following to your ``~/.bashrc`` file:
+
+.. code-block:: console
+
+    gpip() {
+        PIP_REQUIRE_VIRTUALENV="" pip "$@"
+    }
+
+After saving the changes and sourcing your ``~/.bashrc`` file you can now install
+packages globally by running ``gpip install``. You can change the name of the
+function to anything you like, just keep in mind that you will have to use that
+name when trying to install packages globally with pip.