Importing ps_mem in ipython crashes the interpreter

To reproduce
`sudo $(which ipython)`

```
import ps_mem
ps_mem.main()
```

prints to STDOUT the table, but says about STDOUT:

> Error in sys.excepthook:
> 
> Original exception was:

**Using**
Kubuntu 18.04
Linux 5.0.x
iPython 7.12.0
python 3.6.9

However, in python 3 default interpreter works without a crash.