Python PIP Error: Unable to find vcvarsall.bat

While trying to install the Python's PIL package on my Windows 7 machine using pip I came across this error:

Error: Unable to find vcvarsall.bat

Although I had Visual Studio 2010 installed, and made sure the batch file exists and the batch file creates the compilation environment correctly, I still got this error.

Googling the issue brought this question with this specific solution.

The short answer (credits to fmuecke) is to point the environment variable VS90COMNTOOLS to the value of  VS100COMNTOOLS.

SET VS90COMNTOOLS=%VS100COMNTOOLS%

This solved the issue.

-Tal