AttributeError: type object 'Unimplemented' has no attribute 'add_path'

Since updating as follows:

- Chaco ==> 5.0.0
- Enable ==> 5.3.1
- Pyface ==> 7.4.2

my Traits/UI GUI application yields the following error upon launch, from the `enable/savage/svg/backends/kiva/renderer.py` file:

> AttributeError: type object 'Unimplemented' has no attribute 'add_path'

Is this a known issue?

Any ideas about what's going on here?

Thanks!
-db

Here's the full back-trace:

```
Traceback (most recent call last):
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\runpy.py", line 194, in _run_module_as_main
return _run_code(code, main_globals, None,
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\runpy.py", line 87, in _run_code
exec(code, run_globals)
File "C:\Users\capnf\Documents\GitHub\PyBERT\pybert\__main__.py", line 2, in
from pybert.pybert import PyBERT
File "C:\Users\capnf\Documents\GitHub\PyBERT\pybert\pybert.py", line 29, in
from chaco.api import ArrayPlotData, GridPlotContainer
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\chaco\api.py", line 343, in
from chaco.overlays.api import (
File "C:\Users\capnf\anaconda3\envs\pybert-dev\Lib\site-packages\shiboken2\files.dir\shibokensupport\feature.py", line 139, in _import
return original_import(name, *args, **kwargs)
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\chaco\overlays\api.py", line 63, in
from chaco.overlays.layers.api import (
File "C:\Users\capnf\anaconda3\envs\pybert-dev\Lib\site-packages\shiboken2\files.dir\shibokensupport\feature.py", line 139, in _import
return original_import(name, *args, **kwargs)
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\chaco\overlays\layers\api.py", line 11, in
from .status_layer import ErrorLayer, StatusLayer, WarningLayer
File "C:\Users\capnf\anaconda3\envs\pybert-dev\Lib\site-packages\shiboken2\files.dir\shibokensupport\feature.py", line 139, in _import
return original_import(name, *args, **kwargs)
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\chaco\overlays\layers\status_layer.py", line 18, in
from enable.savage.svg.backends.kiva.renderer import Renderer as KivaRenderer
File "C:\Users\capnf\anaconda3\envs\pybert-dev\Lib\site-packages\shiboken2\files.dir\shibokensupport\feature.py", line 139, in _import
return original_import(name, *args, **kwargs)
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\enable\savage\svg\backends\kiva\renderer.py", line 36, in
class CompiledPath(KivaCompiledPath):
File "C:\Users\capnf\anaconda3\envs\pybert-dev\lib\site-packages\enable\savage\svg\backends\kiva\renderer.py", line 38, in CompiledPath
AddPath = KivaCompiledPath.add_path
AttributeError: type object 'Unimplemented' has no attribute 'add_path'
```