Using pyplot@Plots on Julia@spack

 Using pyplot@Plots on Julia installed via spack is a bit complicated.

We first need to setup Python environment
(actually, you may want to use conda provided by Julia, so, you may do
Julia> ENV["PYTHON"]=""
)

as described in the following link;
https://github.com/JuliaPy/PyCall.jl

and then,

Julia> using Plots
Julia> pyplot()