function loadFile(filePath, extension) {

  var content = null;

  // Resolve the path into an absolute path
  filePath = resolveFilePath(filePath, extension);

  // The file doesn't exist
  if (!isFile(filePath)) {
    throw new Error('The provided file doesn\'t exit');
  }

  // Read the file
  try {
    content = di.fs.readFileSync(filePath);
  } catch (error) {
    throw new Error(error);
  }

  return content;

}
Load a file's content

- Check if the file exists, if not found check
  if the file exists with appending the extension

Throws
- The provided file doesn't exit
- Any reading errors

@param  {String} filePath  an absolute or a relative path
@param  {String} extension
@return {String}