Deprecation warning when using kiva explorer with wx backend (among other ETS errors)

When I use the kiva explorer with the wx backend, I see the following deprecation warning printed to the console -

```
C:\Users\rporuri\.edm\envs\enable-test-3.6-wx\lib\site-packages\kiva\agg\plat_support.py:188: wxPyDeprecationWarning: Call to deprecated item. Use GetHandle instead.
self.draw(window_dc.GetHDC(), x, y, width, height)
```

Ref https://wxpython.org/Phoenix/docs/html/wx.DC.html#wx.DC.GetHDC and https://wxpython.org/Phoenix/docs/html/wx.DC.html#wx.DC.GetHandle
Xref https://github.com/enthought/pyface/issues/901 and https://github.com/enthought/traitsui/issues/1535