### About sage.plot.plot.EMBEDDED_MODE

Cantor program used sage-cli, and in this program there is need to disable external viewers.
I found sage variable, which, I hope, will do it: `sage.plot.plot.EMBEDDED_MODE`

.

But after setting `sage.plot.plot.EMBEDDED_MODE`

to `True`

I haven't any changes: external viewer starts, for example, for plots.

But in `src/sage/structure/graphics_file.py`

on line 161 we have `launch_viewer`

function, which, I think, start external viewer and where there is this condition:

```
from sage.plot.plot import EMBEDDED_MODE
if EMBEDDED_MODE:
raise RuntimeError('should never launch viewer in embedded mode')
```

So, as I see, if `sage.plot.plot.EMBEDDED_MODE`

is `True`

, we don't start external viewer, because we exit from function `launc_viewer`

with `RuntimeError`

. But sage works fine with `EMBEDDED_MODE = True`

.
Could anyone explain this behavior, is it a bug with `sage.plot.plot.EMBEDDED_MODE`

or I am wrong?