Adjusted scalatest.scala to fix dependency error when build with Scala 2.13.0-M4, as the starting point to make 3.1.x to work with Scala 2.13.0-M4.
Adjusted scalatest.scala to fix dependency error when build with Scala 2.13.0-M4, as the starting point to make 3.1.x to work with Scala 2.13.0-M4.

scalatest/scalatest,scalatest/scalatest,cheeseng/scalatest,scalatest/scalatest,cheeseng/scalatest,dotty-staging/scalatest,dotty-staging/scalatest,dotty-staging/scalatest,cheeseng/scalatest