bug#30384: additional inputs required for Blender plugins

[Quiliro Ordonez Baca]

I was trying to install Sverchok plugin for Blender. It enables Blender
to change parameters in order to modify a wide range of values without
redrawing everything in case of a global change in something repetitive.

I checked the license. It is GPLv3. What else should i do to verify freedom?

When i tryed to install the Sverchok addon
https://wiki.blender.org/index.php/Extensions:2.6/Py/Scripts/Nodes/Sverchok
http://nikitron.cc.ua/sverch/html/main.html
I got the message:
ImportError: No module named ‘numpy’
so i installed python-numpy.
And then i got error:
ImportError: No module named ‘requests’
I then instaled python-requests. Both these dependencies are mentioned in 
Sverchok's documentation.
The Blender binary ships with:
idna, chardet, urllib3, certifi, requests and numpy
https://git.blender.org/gitweb/gitweb.cgi/blender.git/blob/HEAD:/build_files/build_environment/cmake/versions.cmake
It reports versions of numpy, requests and others
set(REQUESTS_VERSION 2.18.4)
set(NUMPY_VERSION v1.13.1)
set(NUMPY_SHORT_VERSION 1.13)
set(NUMPY_URI 
https://pypi.python.org/packages/c0/3a/40967d9f5675fbb097ffec170f59c2ba19fc96373e73ad47c2cae9a30aed/numpy-1.13.1.zip)
set(NUMPY_HASH 2c3c0f4edf720c3a7b525dacc825b9ae)

propagated-inputs

The NixOS package explicitly disables numpy at build time.

Those dependencies are not required for building the Guix package:
https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/graphics.scm?id=v0.14.0-1266-gd2a7170de#n79
It's better to just package these plugins separately rather than
propagating these (large) packages for every Blender user.
They are not necessary to run blender
https://wiki.blender.org/index.php/Dev:Doc/Building_Blender/Linux/dependencies
It is just that Blender's oficial binary ships with those plugins and
their dependencies by default. We need not do the same. If the user
needs those addons, she may install them with Guix solving the
dependencies.

I was helped by:
<bzztploink>
<Yaniel>
from #blender
and:
<mbakke>
from the Guix.
Thank you very much!