The socketserver module breaks imports on case-insensitive FS

[sergiimk]

We encountered an issue where socketserver module that is installed by future library completely shadows the built-in SocketServer module and breaks imports.

Steps to reproduce

• We use Mac OS which has a case-insensitive file system
• Run a container with your working directory mounted into it

docker run -it --rm -v `pwd`:/opt/x python:2.7.15 bash
$ cd /opt/x/

• Create a venv and install future

$ virtualenv test
$ source test/bin/activate
$$ pip install future
$$ deactivate

• Run following script

import os
import sys

activate_this = '/opt/x/test/bin/activate_this.py'
execfile(activate_this, dict(__file__=activate_this))

import SocketServer
print(SocketServer)

import socketserver
print(socketserver)

print(SocketServer.TCPServer)

Results

The above script is using the activate_this.py method of activating the virtualenv. It's ugly but it is supported. It results in following sys.path:

['/opt/x/test/lib/python2.7/site-packages', '/opt/x', '/usr/local/lib/python27.zip', '/usr/local/lib/python2.7', '/usr/local/lib/python2.7/plat-linux2', '/usr/local/lib/python2.7/lib-tk', '/usr/local/lib/python2.7/lib-old', '/usr/local/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/site-packages']

Note that site-packages dir is searched first.

Both imports result in:

import SocketServer
print(SocketServer)
<module 'SocketServer' from '/opt/x/test/lib/python2.7/site-packages/SocketServer/__init__.pyc'>

import socketserver
print(socketserver)
<module 'socketserver' from '/opt/x/test/lib/python2.7/site-packages/socketserver/__init__.pyc'>

The statement from SocketServer import * inside the socketserver/__init__.py results in module importing itself, so the further attempt to access SocketServer.TCPServer fails.

Expectation

Installing future package doesn't break existing code on case-insensitive file systems.

Note: importing SocketServer from within virtualenv that is activated as source test/bin/activate doesn't result in an issue, since it results (for some reason) in a different sys.path where the system lib directory is searched first, so built-in module is not shadowed.