Python Visual C++ 10.0 required unable to find vcvarsall.bat

To fix the error for Python 2.7 on Windows

error Microsoft Visual C++ 10.0 is required (unable to find vcvarsall.bat)

Install Microsoft Visual C++ Compiler for Python 2.7.

Why?

Visual Studio is used for Python on Windows whenever C, C++, Fortran or other compiled language extension modules are used from Python. For example, a C library may be used for better performance, seamlessly called from Python.