Usage from another addon?

I get can get the repl going from the addon-dir, but how do I use it from another addon?

I tried...

```
~/gits/someaddon $ cfx run --extra-packages=jep4repl
Traceback (most recent call last):
File "/Users/glind/bin/cfx", line 33, in
cuddlefish.run()
File "/Users/glind/gits/addon-sdk/python-lib/cuddlefish/__init__.py", line 626, in run
deps = packaging.get_deps_for_targets(pkg_cfg, targets)
File "/Users/glind/gits/addon-sdk/python-lib/cuddlefish/packaging.py", line 275, in get_deps_for_targets
raise PackageNotFoundError(dep, required_reason)
cuddlefish.packaging.PackageNotFoundError: jep4repl (specified as target)
```