code: protected final File createDirectoryArtifact(final File outputDirectory,
              final String artifact) {
          // Construct artifact path based on output directory
          String path = asPath(outputDirectory.getAbsolutePath(), artifact);
          final File ret = new File(path);
          if (!ret.isDirectory()) {
              // Fail if the directory artifact couldn't be created
              if (!ret.mkdir()) {
                  error(DIRECTORY_CREATION_FAILED + ret);
                  bail(ExitCode.BAD_OUTPUT_DIRECTORY);
              }
          }
          return ret;
      }
docs: Creates the directory artifact, failing if the directory couldn't be
  created.
  
  @param outputDirectory Phase output directory
  @param artifact Directory artifact to be created