Pip error even Microsoft Visual C++ 14.0 is installed

This problem was solved on a computer having Visual Studio Community 2017 v15.5.2 and the Visual Studio Installer v1.16.1247.518 installed.

The steps used are as follows:

1. Start the Visual Studio Installer
2. Visual Studio Installer showed a Installed section that stated that Visual Studio Community 2017. In that section was a drop-down titled More. The drop- down option Modify was selected.
3. Visual Studio Installer then showed "tabs" titled Workloads, Individual components, Language packs and Installed locations. The tab Individual components was selected.
4. Scrolling down the list of Individual components, there was a section titled Compilers, build tools, and runtimes. Under that section there was a VC++ 2015.3 v140 toolset for desktop (x86,x64) option that was unchecked. The option was then checked.
5. The Modify button located at the lower right part of the Visual Studio Installer was pushed.
6. After waiting an unreasonably long amount of time, the installer finished modifying the installation of Visual Studio Community 2017.

As always, your mileage may differ.

As per instructions here: https://www.scivision.co/python-windows-visual-c++-14-required/

Use vs_buildtools.exe and install only the windows 10 SDK.