pip gets broken(?) by pip install --upgrade pip virtualenv

[vdmz]

Thanks for this helpful little repo, btw.
I was trying to build a kern-3 image because some things I need are not yet in kern-4.
I wanted to add a further pip package, so I appended this line to the Singularity file

pip install astLib

and was rewarded with (at the end of a lengthy image build)

+ pip install astLib
Traceback (most recent call last):
  File "/usr/bin/pip", line 9, in <module>
    from pip import main
ImportError: cannot import name main
ABORT: Aborting with RETVAL=255
Cleaning up...

Why this is needed in the Singularity file?

pip install --upgrade pip virtualenv

Discussion of this issue here suggests it's not good practice:

• pip v10 breaks Debian/Ubuntu pip3 command pypa/pip#5221
• Upgrade Message on Linux (and talking to Linux Vendors) pypa/pip#5346
• ImportError in system pip wrappers after an upgrade pypa/pip#5599

I was able to add the extra module with

python -m pip install astLib

[gijzelaerr]

What is missing in KERN-4 exactly? You can make an issue for that if you want.

Thanks for reporting, i'll remove the installation of pip, then the user can decide what needs to happen.

[gijzelaerr]

btw it is a path issue, /usr/local/bin should be looked at before /usr/bin, but somehow that doesn't happen inside the container. If you do /usr/local/bin/pip install etc it works.