build fails with cannot import name '_datatable'

[jangorecki]

reproducible example isolated in fresh docker image

docker pull ubuntu:16.04
docker run -it --rm ubuntu:16.04 /bin/bash
apt-get update
apt-get install -y python3 python3-pip git
pip3 install git+https://github.com/h2oai/datatable
#  Running setup.py install for datatable ... done
#Successfully installed blessed-1.16.1 colorama-0.4.3 datatable-0.11.0a0 six-1.13.0 typesentry-0.2.7 wcwidth-0.1.7
python3
import datatable as dt
#Python 3.5.2 (default, Oct  8 2019, 13:06:37) 
#[GCC 5.4.0 20160609] on linux
#Type "help", "copyright", "credits" or "license" for more information.
#>>> import datatable as dt
#Traceback (most recent call last):
#  File "<stdin>", line 1, in <module>
#  File "/usr/local/lib/python3.5/dist-packages/datatable/__init__.py", line 24, in <module>
#    from .frame import Frame
#  File "/usr/local/lib/python3.5/dist-packages/datatable/frame.py", line 23, in <module>
#    from datatable.lib._datatable import Frame
#  File "/usr/local/lib/python3.5/dist-packages/datatable/lib/__init__.py", line 31, in <module>
#    from . import _datatable as core
#ImportError: cannot import name '_datatable'

setting high priority because datatable is already lagged behind for 2 weeks on https://h2oai.github.io/db-benchmark/

[st-pasha]

I checked that after #2276 the install works; however you need pip version ~20.0, the version that comes from apt-get is ancient 8.1.1.
In order to get the latest version of pip you can run

pip3 install git+https://github.com/pypa/pip

before trying to install datatable.

[jangorecki]

Thanks, looks like pip 20.0 should be soon released: pypa/pip#7531

[mgalyean]

I posted a similar issue and am trying to resolve using info given here. I'm pretty much on a python3 environment so am vexed. When directed to use pip, does that mean pip3? If it means the old pip, does that mean I'm supposed to have python2 installed and use the pip from 2? Should pip just be a symlink to pip3 in my env? The version of pip3 in debian main now is 18.1-5, is the reference to pip 20ish meaning a later version of pip3? Sorry if all this is crystal clear to others who breathe it day in and out but I'm just trying to focus on what I'm building and getting rabbit-holed into minor version diffs of the lower toolchain and not faring well with my main task at this point