readDataFile (Just userDir) fname = do
  exists <- doesFileExist (userDir </> fname)
  if exists
     then BS.readFile (userDir </> fname)
     else readDefaultDataFile fname

-- | Same as 'readDataFile' but returns a String instead of a ByteString.
readDataFile (Just userDir) fname = do
  exists <- doesFileExist (userDir </> fname)
  if exists
     then BS.readFile (userDir </> fname)
     else readDefaultDataFile fname

-- | Same as 'readDataFile' but returns a String instead of a ByteString.
readDataFile (Just userDir) fname = do
  exists <- doesFileExist (userDir </> fname)
  if exists
     then BS.readFile (userDir </> fname)
     else readDefaultDataFile fname

-- | Same as 'readDataFile' but returns a String instead of a ByteString.