BuildImage can return false for lots of reasons. Log two of the more
plausible ones. You'll still need to edit this file and pass True to
RunCommand to work out *what* went wrong, but at least this logging will
tell you *where* things went wrong.
Bug: http://b/63142920
Test: debugged my actual problem
Change-Id: If84427058108dcac0a1b5e2216b8bb11eef522ca