nbconvert disabled in IPython 5.1.0 easyconfig using Python 2.7.12

[boegel]

I was forced to exclude the nbconvert extension from the IPython 5.1.0 easyconfig using Python 2.7.12 as a base in #3823, because it was responsible for the sanity check failing.

Any sanity check command trying to access the IPython module failed with an error like this:

== 2016-11-17 16:36:01,157 extensioneasyblock.py:136 WARNING Sanity check for ipywidgets failed: ipywidgets failed to install, cmd 'python -c 'import ipywidgets'' (stdin: None) output: Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/ipywidgets/__init__.py", line 20, in <module>
    from IPython import get_ipython
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/IPython/__init__.py", line 48, in <module>
    from .core.application import Application
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/IPython/core/application.py", line 25, in <module>
    from IPython.core import release, crashhandler
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/IPython/core/crashhandler.py", line 28, in <module>
    from IPython.core import ultratb
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/IPython/core/ultratb.py", line 128, in <module>
    from IPython.utils.terminal import get_terminal_size
  File "/user/home/gent/vsc400/vsc40023/eb_phanpyscratch/CO7/haswell-ib/software/IPython/5.1.0-intel-2016b-Python-2.7.12/lib/python2.7/site-packages/IPython/utils/terminal.py", line 22, in <module>
    from backports.shutil_get_terminal_size import get_terminal_size as _get_terminal_size
ImportError: No module named shutil_get_terminal_size

The problem was that the entrypoints Python package (https://pypi.python.org/pypi/entrypoints), which is required for nbconvert, pulls in the configparser package (https://pypi.python.org/pypi/configparser) as a dependency, which also provides a backports package.

The import from backports.shutil_get_terminal_size fails because it is hitting the backports namespace provided by configparser rather than the one provided by the backports.shutil_get_terminal_size package (https://pypi.python.org/pypi/backports.shutil_get_terminal_size).

At this time, I have no idea why this suddenly pops up now, especially since the tests reports in #3424 show that this originally was no problem, even though all components responsible for this problem were already included...

[boegel]

fixed in #4504