Tkinter: "Python may not be configured for Tk"

Under Arch/Manjaro just install the package tk:

sudo pacman -S tk

Install tk-devel (or a similarly-named package) before building Python.

Solution for MacOS

After trying a bunch of things, this is how it finally worked:

$ brew install python-tk

According to http://wiki.python.org/moin/TkInter :

If it fails with "No module named _tkinter", your Python configuration needs to be modified to include this module (which is an extension module implemented in C). Do not edit Modules/Setup (it is out of date). You may have to install Tcl and Tk (when using RPM, install the -devel RPMs as well) and/or edit the setup.py script to point to the right locations where Tcl/Tk is installed. If you install Tcl/Tk in the default locations, simply rerunning "make" should build the _tkinter extension.