private void ValidateLicenseFile(IEnumerable <IPackageFile> files, LicenseMetadata licenseMetadata)
 {
     if (!PackageTypes.Contains(PackageType.SymbolsPackage) && licenseMetadata?.Type == LicenseType.File)
     {
         var ext = Path.GetExtension(licenseMetadata.License);
         if (!string.IsNullOrEmpty(ext) &&
             !ext.Equals(".txt", StringComparison.OrdinalIgnoreCase) &&
             !ext.Equals(".md", StringComparison.OrdinalIgnoreCase))
         {
             throw new PackagingException(NuGetLogCode.NU5031, string.Format(CultureInfo.CurrentCulture, NuGetResources.Manifest_LicenseFileExtensionIsInvalid, licenseMetadata.License));
         }
         var strippedLicenseFileLocation = PathUtility.StripLeadingDirectorySeparators(licenseMetadata.License);
         var count = files.Where(e => PathUtility.StripLeadingDirectorySeparators(e.Path).Equals(strippedLicenseFileLocation, PathUtility.GetStringComparisonBasedOnOS())).Count();
         if (count == 0)
         {
             throw new PackagingException(NuGetLogCode.NU5030, string.Format(CultureInfo.CurrentCulture, NuGetResources.Manifest_LicenseFileIsNotInNupkg, licenseMetadata.License));
         }
     }
 }