Hey,

I've been trying to get threejs output working for a few days now. My current installation is from Conda-Forge (sage 8.3) and I'm on MacOS High Sierra (10.13.6).

In the sage repl if I run

```
P = parametric_plot3d([cos(x),sin(x),x/10], (x,0,4*pi)
P.show(viewer='threejs')
```

sage raises `ImportError: cannot import name 'THREEJS_DIR'`

. Full output: paste2.org/vP4nBZ9A

If I run

```
P = parametric_plot3d([cos(x),sin(x),x/10], (x,0,4*pi)
P.show(viewer='threejs', online=True)
```

sage returns `Launched html viewer for Graphics3d Object`

, but nothing actually happens on my machine. No browser opens, nothing noticeable. I have tried changing the default viewer browser, but it has not made a difference. I'm at a loss as to what is going on here.

Finally, if I run it in a jupyter notebook,

```
p1 = sphere(color='red', opacity='.5')
p2 = sphere((-1,-1,1), color='cyan', opacity='.3')
p3 = sphere((1,-1,-1), color='yellow', opacity='.7')
show(p1 + p2 + p3, viewer='threejs', online=True)
```

I get `TypeError: a bytes-like object is required, not 'str'`

.
Full traceback here: paste2.org/c1VLUmNm

I've tried pretty hard to diagnose exactly what's going on, but I can't seem to find any recent documentation relating to this issue. My best guess is that the paths are getting messed up because I'm running sage through an anaconda environment. Is there any way to fix this? That being said, I was having similar issues before and wanted to integrate with jupyter which lead to me moving to anaconda. I am going to try and reinstall sage outside of anaconda and see if I can get it to work there, but I figured I should post first because I'm pretty stuck, and having everything in anaconda would be much nicer if possible.