The issue arises by simply calling configure on the Scale widget of the themed tk (ttk) widgets set:

```
cursor = scale.configure('cursor')[-1]
```

The above casues the following error:

```
File "C:\Users\Giovanni\Tests\test_scale.py", line 604, in main
    cursor = scale.configure('cursor')[-1]
File "C:\Users\Giovanni\AppData\Local\Programs\Python\Python37\lib\tkinter\ttk.py", line 1090, in configure
    kw.update(cnf)
ValueError: dictionary update sequence element #0 has length 1; 2 is required
```

The interpreter is:

```
Python 3.7.4 (tags/v3.7.4:e09359112e, Jul  8 2019, 20:34:20) [MSC v.1916 64 bit (AMD64)] on win32```