aio app init fails if the stored IMS token is invalid

**Describe the bug**
`aio app init` fails with a non-friendly user-message if the stored IMS token is invalid.

**To Reproduce**
Edit your global `.aio` config file containing a persisted IMS token after a successful `aio login`.
Modify the token.
Try `aio app init`
The CLI outputs an error message but there's no solution proposed to the end-user

**Expected behavior**
As an end-user, I'd expect at least to know what to do (i.e. `aio login` again).
We could also run `aio login` automatically such as it is the case when the token has expired.