Report errors when dependency resolution fails (#71)

* Report errors when dependency resolution fails

Function `Lib.reolveDependencies` now checks the result of the coursier dependency
resolution for errors. The return value of the fuction is now a
`Result[Seq[PathRef]]` and errors are signaled by returning an instance
of Failure when errors occur while resolving dependencies.

`ScalaModule` now has a new task called `resolve` which allows for
triggering dependency resolution directly from the cmd line like:
`mill run resolve`.

`ResolveDepsTests` was added to verify failed resolution is properly
detected and reported.

* Remove type signatures in ScalaModule.scala

* Updates from PR comments

1 files changed, 3 insertions, 0 deletions

diff --git a/scalaplugin/src/test/resource/resolve-deps/src/main/scala/Main.scala b/scalaplugin/src/test/resource/resolve-deps/src/main/scala/Main.scala
new file mode 100644
index 00000000..5dcbe39a
--- /dev/null
+++ b/scalaplugin/src/test/resource/resolve-deps/src/main/scala/Main.scala
@@ -0,0 +1,3 @@
+object Main {
+  println("ResolveDeps Main: hello world!")
+}