ModuleNotFoundError, even though I can see module in dist-packages folder, Setuptools / EGG issue?

[John Ladasky]

On Wednesday, April 8, 2020 at 10:47:42 AM UTC-7, John Ladasky wrote:
> Hi folks,
> 
> Something broke in my Python installation in the past two or three days.  I'm working in Ubuntu 19.10 and Python 3.7, without virtual environments.  
> 
> I have two modules of Python source code that I am developing.  I regularly change this code and "distribute" it to myself using setuptools.  From the command prompt in the module's base folder, I execute:
> 
>   python3 setup.py sdist
>   sudo python3 setup.py install
> 
> That process has been working for me for years.  But after recent rebuilds, when I try to import those modules today, I get ModuleNotFoundErrors for each of them.  I tried importing other modules that were installed by pip3.  They work fine.
> 
> I looked in /usr/local/lib/python3.7/dist-packages.  The one thing that is unique to my two packages is the .egg extension at the end of the file names.  Oddly, one of the two modules is a single .egg archive file, and the other is a normal folder with folders inside it, despite the .egg extension in the name.
> 
> A third package of mine which I did not build recently appears as a normal sub-folder within dist-packages, and it imports correctly.
> 
> What is setuptools supposed to do?  Why has its behavior apparently changed?  Hope someone can offer some advice.  Thanks.

Followup observation:

One of the two Python packages I'm building using setuptools depends on argparse 1.4.  The default version of argparse in my Python 3.7 distro is 1.1. 
 I watched setuptools fetch argparse 1.4 from the Net when I built it.

When I start my Python interpreter and import argparse, I get version 1.1.

I found an argparse 1.4 sub-folder in my site-packages folder.  It was built yesterday.  It has a .egg extension, just like my two modules that won't import.