import error when using submission widget

[jdcourcol]

I ran through notebook week 3. Graded exercise as a newly created user:

[antonelepfl]

@wvangeit
If we put the pip install and the import of the submission widget on the very top of the notebook (before !pip install -q bluepyopt==1.5.12 matplotlib==2.0.2 numpy==1.13.0)
And then in the end we just call the widget the error disappears.
Could you change that please?

[wvangeit]

ok, interesting .... will have a look

[wvangeit]

Do we know 'why' this happens ?
Not sure we should try to fix it before we know it won't affect other things

[wvangeit]

Ok, we figured out why this happens. For future reference, the 'import neuron' statement sets the PYTHONHOME variable, and this messes up the pip / virtualenv in the collab.
To solve this, one should run:

import os
os.unsetenv('PYTHONHOME')

before every pip (or after importing neuron)