Improve resolve exception

fixes #1422, #381 

## steps

```scala
lazy val d = project.
  settings(
    libraryDependencies += "org.apache.cayenne.plugins" % "maven-cayenne-plugin" % "3.0.2"
  )
```

## problem

You have no idea which transitive deps path failed.

## what this changes

```
[warn] 	::::::::::::::::::::::::::::::::::::::::::::::
[warn] 	::          UNRESOLVED DEPENDENCIES         ::
[warn] 	::::::::::::::::::::::::::::::::::::::::::::::
[warn] 	:: foundrylogic.vpp#vpp;2.2.1: not found
[warn] 	::::::::::::::::::::::::::::::::::::::::::::::
[warn] 
[warn] 	Note: Unresolved dependencies path:
[warn] 		foundrylogic.vpp:vpp:2.2.1
[warn] 		  +- org.apache.cayenne:cayenne-tools:3.0.2
[warn] 		  +- org.apache.cayenne.plugins:maven-cayenne-plugin:3.0.2
[warn] 		  +- d:d_2.10:0.1-SNAPSHOT
```
I'm guessing you picked it up when you saw `findPath`, but the imple of `findPath` is what I'm worried.