I installed a new module and it appears as if one of its dependencies was not already installed. The module is called Xlib.display. Here is the error message I received:
I was looking for the same answer, however after some more digging it seems that XCB (X protocol C-language Binding) will obsolete Xlib in general. From the XCB website:
The X protocol C-language Binding (XCB) is a replacement for Xlib featuring a small footprint, latency hiding, direct access to the protocol, improved threading support, and extensibility.
Fortunately there are python bindings available as python-xpyb in apt or xpyb on PyPi. I've not gotten that far in my project so I haven't tested if this works with Python3, but this is probably the way to go and the proper place to file any Python3 support bugs if necessary.