Test: System.CodeDom.Tests.TempFileCollectionTests/AddExtension_InvalidFileExtension_ThrowsArgumentException failed with "System.ArgumentNullException"

Opened on behalf of @JiayiLi1

The test System.CodeDom.Tests.TempFileCollectionTests/AddExtension_InvalidFileExtension_ThrowsArgumentException(fileExtension: \"\") has failed.

Assert.Throws() Failure\r
Expected: typeof(System.ArgumentException)\r
Actual: typeof(System.ArgumentNullException): Value cannot be null.\r
Parameter name: format

    Stack Trace:

       at System.String.FormatHelper(IFormatProvider provider, String format, ParamsArray args)
   at System.String.Format(String format, Object arg0)
   at System.SR.Format(String resourceFormat, Object p1)
   at System.CodeDom.Compiler.TempFileCollection.AddExtension(String fileExtension, Boolean keepFile)
   at System.CodeDom.Compiler.TempFileCollection.AddExtension(String fileExtension)
   at System.CodeDom.Tests.TempFileCollectionTests.<>c__DisplayClass21_0.<AddExtension_InvalidFileExtension_ThrowsArgumentException>b__0()

Build : Master - 20170609.02 (UWP F5 Tests)
Failing configurations:

• Windows.10.Amd64-x64
  • Debug
  • Release

Detail: https://mc.dot.net/#/product/netcore/master/source/official~2Fcorefx~2Fmaster~2F/type/test~2Ffunctional~2Fuwp~2F/build/20170609.02/workItem/System.CodeDom.Tests/analysis/xunit/System.CodeDom.Tests.TempFileCollectionTests~2FAddExtension_InvalidFileExtension_ThrowsArgumentException(fileExtension:%20%5C%22%5C%22)

[KristinXie1]

Failed tests:
AddExtension_InvalidFileExtension_ThrowsArgumentException
AddFile_DuplicateFileName_ThrowsArgumentException
AddFile_InvalidFileName_ThrowsArgumentException

[KristinXie1]

This issue is not repro on recent builds, If it happens again, will reopen it.