Release the lock on the file.

  Args:
    fd: int, the file descriptor of the file to unlock.
    path: string, the name of the file to lock.

  Raises:
    IOError, raised from flock while attempting to release a file lock.

def Unlock(fd, path):
  """Release the lock on the file.

  Args:
    fd: int, the file descriptor of the file to unlock.
    path: string, the name of the file to lock.

  Raises:
    IOError, raised from flock while attempting to release a file lock.
  """
  try:
    fcntl.flock(fd, fcntl.LOCK_UN | fcntl.LOCK_NB)
  except IOError as e:
    if e.errno == errno.EWOULDBLOCK:
      raise IOError('Exception unlocking %s. Locked by another process.' % path)
    else:
      raise IOError('Exception unlocking %s. %s.' % (path, str(e)))