I did a quick port of the two Home Assistant related plugins to Python 3, and so far they seem to be working OK. I'm trying to get an idea of how many people use these Plugins, or Home Assistant in general, to see if it's worth spending any more time on them.
"Home Assistant" is the plugin that pulls (imports) HA devices into Indigo. Useful if you have devices that are supported by HA, but not by Indigo. Currently works by polling HA for the status of each device, so it's not very efficient and there's a delay from device status change to showing up in Indigo. It looks like it's possible to update this to a websocket connection to HA, which would be more efficient with faster response.
"HassBridge" is the plugin that lets you push (export) Indigo devices to HA. Useful if you want to use these devices in an HA dashboard. But it's device support is VERY limited, basically Insteon and Z-Wave and not much else. Use MQTT for bi-directional communication to HA, so device commands from HA do get relayed to Indigo, as well as device status changes from Indigo to HA.