The following BasicCommandLineTest unit tests fail when run under the es-ES locale:

• Microsoft.CodeAnalysis.VisualBasic.CommandLine.UnitTests.CommandLineTests.RefOutWithError
  Message:

    Assert.Equal() Failure
                                     ↓ (pos 134)
    Expected: ···rror BC30451: 'Bad' is not declared. It may be inaccessible d···
    Actual:   ···rror BC30451: 'Bad' no está declarado. Puede que sea inaccesi···
                                     ↑ (pos 134)
  

  Stack trace:

   en Xunit.Assert.Equal(String expected, String actual, Boolean ignoreCase, Boolean ignoreLineEndingDifferences, Boolean ignoreWhiteSpaceDifferences)
   en Xunit.Assert.Equal(String expected, String actual)
   en Microsoft.CodeAnalysis.VisualBasic.CommandLine.UnitTests.CommandLineTests.RefOutWithError()
  

Full details in: Roslyn.Compilers.VisualBasic.CommandLine.UnitTests.dll.zip