steps

Travis CI gets into some situation where sbt launcher fails to resolve the sbt core artifacts correctly.

Here's a repro. Save the following to /tmp/launchertest/launchconfig

[scala]
  version: auto
[app]
  version: 2.14.6
  org: jline
  name: jline
  class: scala.App
  cross-versioned: false

[repositories]
  local
  maven-central
  sonatype-releases: https://oss.sonatype.org/content/repositories/releases/
[boot]
  directory: /tmp/boot

Then run:

$ java -jar ~/work/sbt-modules/launcher/target/sbt-launch-1.1.1.jar @/tmp/launchertest/launchconfig

problem

error during sbt execution: No Scala version specified or detected

"Error during sbt execution: No Scala version specified or detected" is misleading since it sounds like ++2.12.8 is missing.

expectation

Improve the error to suggest that something wrong happened with the launcher.

workaround for Travis CI

If you are caching ~/.sbt/, wipe out the cache and try again.