julia.core.JuliaError: Exception 'LoadError: LoadError: InitError: UndefVarError: python not defined

**Code:**
```
from julia import Main
demux = Main.using("NextGenSeqUtils.deMux")
```

**Error:**
```
Traceback (most recent call last):
File "/home/dean/src/work/PacBio_processing_pipeline/singularity/test_julia.py", line 2, in
demux = Main.using("NextGenSeqUtils.deMux")
File "/home/dean/.local/share/virtualenvs/PacBio_processing_pipeline-MGndRJCW/lib/python3.7/site-packages/julia/core.py", line 790, in using
self.eval("using %s" % module)
File "/home/dean/.local/share/virtualenvs/PacBio_processing_pipeline-MGndRJCW/lib/python3.7/site-packages/julia/core.py", line 769, in eval
ans = self._call(src)
File "/home/dean/.local/share/virtualenvs/PacBio_processing_pipeline-MGndRJCW/lib/python3.7/site-packages/julia/core.py", line 702, in _call
self.check_exception(src)
File "/home/dean/.local/share/virtualenvs/PacBio_processing_pipeline-MGndRJCW/lib/python3.7/site-packages/julia/core.py", line 752, in check_exception
.format(exception, src))
julia.core.JuliaError: Exception 'LoadError: LoadError: InitError: UndefVarError: python not defined
during initialization of module PyPlot
while loading /home/dean/.julia/v0.6/NextGenSeqUtils/src/include_all.jl, in expression starting on line 12
while loading /home/dean/.julia/v0.6/NextGenSeqUtils/src/NextGenSeqUtils.jl, in expression starting on line 2' occurred while calling julia code:
using NextGenSeqUtils.deMux
```

**To install NextGenSeqUtils, in Julia shell:**
if Pyplot is not installed before:
```
ENV["PYTHON"]=""
```
else:
```
ENV["PYTHON"]="/path/to/python/used/with/pyplot"
```

and then:
```
Pkg.update(); Pkg.clone("https://github.com/MurrellGroup/NextGenSeqUtils.jl"); using NextGenSeqUtils
```