我参加了斯卡拉课程。我下载了示例项目，但我无法编译它。运行控制台命令时给我错误。
build.sbt：
name := course.value + "-" + assignment.value
scalaVersion := "2.12.4"
scalacOptions ++= Seq("-deprecation")
// grading libraries
libraryDependencies += "junit" % "junit" % "4.10" % Test
// for funsets
libraryDependencies += "org.scala-lang.modules" %% "scala-parser-combinators" % "1.0.4"
resolvers += "Artima Maven Repository" at "http://repo.artima.com/releases"
// include the common dir
commonSourcePackages += "common"
courseId := "bRPXgjY9EeW6RApRXdjJPw"
错误：
> console
[info] Updating root
[info] Resolved root dependencies
[trace] Stack trace suppressed: run last *:coursierResolution for the full output.
[error] (*:coursierResolution) coursier.ResolutionException: Encountered 1 error(s) in dependency resolution:
[error] org.scalatest:scalatest_2.12:2.2.4:
[error] not found:
[error] /Users/joaonobre/.ivy2/local/org.scalatest/scalatest_2.12/2.2.4/ivys/ivy.xml
[error] /Users/joaonobre/.sbt/preloaded/org.scalatest/scalatest_2.12/2.2.4/ivys/ivy.xml
[error] /Users/joaonobre/.sbt/preloaded/org/scalatest/scalatest_2.12/2.2.4/scalatest_2.12-2.2.4.pom
[error] https://repo1.maven.org/maven2/org/scalatest/scalatest_2.12/2.2.4/scalatest_2.12-2.2.4.pom
[error] http://repo.artima.com/releases/org/scalatest/scalatest_2.12/2.2.4/scalatest_2.12-2.2.4.pom
[error] Total time: 1 s, completed Dec 22, 2017 4:16:17 PM
scala -version
Scala code runner version 2.12.4 -- Copyright 2002-2017, LAMP/EPFL and Lightbend, Inc.
知道怎么解决吗？
感谢。