Issue
I was using Tox to test python2.7. Python2.7 testing was executed via the "py27" environment. If I ran
$ tox -e py27
I received the following error traceback:
Traceback (most recent call last): File ".tox/py27/bin/pip", line 7, in <module> from pip import main File "/home/username/projects/argh/.tox/py27/lib/python2.7/site-packages/pip/__init__.py", line 13, in <module> from pip.utils import get_installed_distributions, get_prog File "/home/username/projects/argh/.tox/py27/lib/python2.7/site-packages/pip/utils/__init__.py", line 15, in <module> import zipfile File "/usr/local/lib/python2.7/zipfile.py", line 6, in <module> import io File "/usr/local/lib/python2.7/io.py", line 51, in <module> import _io ImportError: /home/username/projects/argh/.tox/py27/lib/python2.7/lib-dynload/_io.so: undefined symbol: _PyErr_ReplaceException
Cause of the issue
This can happen if you upgrade your Python version corresponding to the tox test. In my case, I had upgraded python2.7 after tox had created its local copy within the .tox tox uses directory.
To verify this was the issue, I determined the version of python2.7 running on my system.
$ python2.7 --version
The response was
Python 2.7.10
But when I ran
$ .tox/py27/bin/python --version
The response was
Python 2.7.9
Solution
The easiest thing to do is just remove the .tox directory within your project and rebuild by rerunning the test for that environment.
$ rm -rf .tox
Be sure to also clear out the .pyc files that were generated by the old python
version
$ find . -type f -name "*.pyc" -exec rm {} \;
Verification
$ .tox/py27/bin/python --version
Python 2.7.10
Woo!