WDS Warnings while compiling - webpack-dev-server

Question

If I define a bare scalajs build.sbt as below with no actual scala code (App is an empty class):
enablePlugins(ScalaJSBundlerPlugin)
lazy val repro = project.in(file(".")).settings(
name := "Repro",
scalaVersion := "2.12.8",
libraryDependencies ++= Seq(
"org.scala-js" %%% "scalajs-dom" % "0.9.6"
),
mainClass in Compile := Some("App"),
scalaJSUseMainModuleInitializer := true,
webpackDevServerPort := 3000
)
with the following two plugins:
addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.27")
addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.15.0")
Then whenever I rung fastOptJS::startWebpackDevServer I get a pile of warnings like below. Is there anything I can do to get rid of these warnings?
[WDS] Warnings while compiling. client:147
./repro-fastopt.js (Emitted value instead of an instance of Error)
Cannot find source file
'https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Boolean.scala':
Error: Can't resolve
'./https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Boolean.scala'
in '/home/des/workspace/repro/target/scala-2.12/scalajs-bundler/main'
# multi (webpack)-dev-server/client?http://localhost:3000
./repro-fastopt.js client:153
./repro-fastopt.js (Emitted value instead of an instance of Error)
Cannot find source file
'https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Byte.scala':
Error: Can't resolve
'./https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Byte.scala'
in '/home/des/workspace/repro/target/scala-2.12/scalajs-bundler/main'
# multi (webpack)-dev-server/client?http://localhost:3000
./repro-fastopt.js client:153
./repro-fastopt.js (Emitted value instead of an instance of Error)
Cannot find source file
'https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Character.scala':
Error: Can't resolve
'./https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Character.scala'
in '/home/des/workspace/repro/target/scala-2.12/scalajs-bundler/main'
# multi (webpack)-dev-server/client?http://localhost:3000
./repro-fastopt.js client:153
./repro-fastopt.js (Emitted value instead of an instance of Error)
Cannot find source file
'https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Class.scala':
Error: Can't resolve
'./https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Class.scala'
in '/home/des/workspace/repro/target/scala-2.12/scalajs-bundler/main'
# multi (webpack)-dev-server/client?http://localhost:3000
./repro-fastopt.js client:153
./repro-fastopt.js (Emitted value instead of an instance of Error)
Cannot find source file
'https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Double.scala':
Error: Can't resolve
'./https://raw.githubusercontent.com/scala-js/scala-js/v1.0.0-M7/javalanglib/src/main/scala/java/lang/Double.scala'
in '/home/des/workspace/repro/target/scala-2.12/scalajs-bundler/main'
...