Unknown capability instance: ''

[wjwwood]

This error message gets printed every time I run the capability server. I've seen this in a catkin workspace with several interfaces and providers, and I'm able to reproduce it on a workspace with no capabilities or providers:

jbinney@h-> rosrun capabilities capability_server 
[WARN] [WallTime: 1391825562.852679] [0.000000] No runnable Capabilities loaded.
[INFO] [WallTime: 1391825562.868363] [0.000000] Capability Server Ready
[ERROR] [WallTime: 1391825562.869098] [0.000000] Unknown capability instance: ''

It looks like on startup the following event message comes out on /capability_server/events:

header: 
  seq: 1
  stamp: 
    secs: 0
    nsecs: 0
  frame_id: ''
capability: ''
provider: ''
type: "server_ready"
pid: 0

And the capability field being an empty string confuses the event handler: https://github.com/osrf/capabilities/blob/master/src/capabilities/server.py#L476

[jonbinney]

It doesn't appear to actually break anything, just an unexpected error message.

[wjwwood]

Right you are, I added that event to make the tests more robust, but ended up missing a check for it there, thanks for catching that.

Converted to a pull request.