docs: protected InputStream initInput(final File file)
          throws MojoExecutionException {
          InputStream stream = null;
          try {
              if (file.isDirectory()) {
                  throw new MojoExecutionException("File "
                      + file.getAbsolutePath()
                      + " is directory!");
              }
              if (!file.exists()) {
                  throw new MojoExecutionException("File "
                      + file.getAbsolutePath()
                      + " does not exist!");
              }
              stream = new FileInputStream(file);
              //append to outfile here
          } catch (FileNotFoundException e) {
              throw new MojoExecutionException("Could not find file: "
                  + file.getAbsolutePath(), e);
          }
          return stream;
      }