"Already up-to-date" and "Run 'yarn' to install missing dependencies"?

I've got a bit of a weird situation where "ember s" reports "Missing yarn packages" followed by a list of missing packages (two of them) and then "Run 'yarn' to install missing dependencies".

However when I run 'yarn' I get the message "success Already up-to-date" .

Any ideas how to get out of this circle ?

---

There's something I did immediately before this started which I guess is the source of my problem

Getting rid of an Add-on

I had installed an Ember Add-on which had generated problems so I decided to get rid of it . To do that I did the following :

git push -f origin 913c2dee12b0363df0664c9c63e0443abe0adb57:foo-bar
git reset --hard 913c2dee12b0363df0664c9c63e0443abe0adb57
yarn
yarn install
yarn clean
yarn install
yarn

Where 913c2dee12b0363df0664c9c63e0443abe0adb57 was the last commit before the unwanted add-on was installed. I don't think there was anything wrong in doing that but now I'm wondering.

---

Output of running Ember Server

When I run 'ember s' I get this output ...

DEPRECATION: ember-cli-babel 5.x has been deprecated. Please upgrade to at least ember-cli-babel 6.6. Version 5.2.8 located: foobar -> ember-cli-build-date -> ember-cli-babel

Missing yarn packages:
Package: @bower_components/jquery
  * Specified: jquery/jquery-dist#
  * Installed: (not installed)

Package: @bower_components/jstree
  * Specified: vakata/jstree#^3.3.5
  * Installed: (not installed)

Run `yarn` to install missing dependencies.



Stack Trace and Error Report: /tmp/error.dump.33c6e8c0abc9fc8abd355dc080268f9c.log
An error occurred in the constructor for ember-cli-dependency-checker at /media/mint/dev/foobar/node_modules/ember-cli-dependency-checker

---

Warning about ember-cli versions

I don't think this is relevant but just for completeness

Running the 'yarn' results in the following appearing in the output text ...

warning foobar@0.0.0: "dependencies" has dependency "ember-cli" with range "~3.8.1" that collides with a dependency in "devDependencies" of the same name with version "3.8"