Comment 4 for bug 1617879

I think the best option here is to find out if codetree really needs a more recent version of charm-tools than is in trusty, or if we can support the stock trusty version as well. If we can support that, let's do so. If we can't, let's update codetree to fail gracefully if you don't have a recent enough version of charm-tools installed (i.e. fall back to using the non charm-tools way of grabbing charms from the charmstore). It should also give a user-friendly warning message that this is the case.

We can then install a more recent version of charm-tools (likely using the classic snap) in places where we need to use private charms.