Better output for cascading failures

[rebeccaskinner]

When we have a node high up in the dependency graph that fails, causing cascading failures due to failing dependencies, it can be difficult to search through the children failing to find the actual failures. I propose that failures due to a failing dependency be condensed into a single output so that the most visible output are the actual failures.

Example:

root/wait.query.git-installed:
 Messages:
 Has Changes: no
 Changes: No changes

root/file.directory.gosrc:
 Error: root/file.directory.gosrc still has changes after apply: mkdir /root/go/src/github.com: no such file or directory
 Messages:
 Has Changes: yes
 Changes: No changes

root/wait.query.go-installed:
 Error: root/wait.query.go-installed still has changes after apply
 Messages:
  Failed after 60 retries (2m2.438849113s)
  Last attempt: check (returned: 1)

Failed due to failing dependency:
  - root/task.install gas
  - root/task.install goconvey
  - root/task.install gosimple
  - root/task.install golint
  - root/task.install goimports
  - root/task.install aligncheck
  - root/task.install varcheck
  - root/task.install panicparse
  - root/task.install gotool
  - root/task.install structcheck
  - root/task.install uconvert
  - root/task.install go guru
  - root/file.directory.gobin

Summary: 2 errors, 2 changes, 14 dependency errors

[stevendborrelli]

I've run into this issue too. This seems like a good first idea of a solution.