sparv_languages() does not propagate errors

[anne17]

Got a crash and this error instead of a proper response:

  Exception ignored in: <function _after_fork at 0x7f998546adc0>
  Traceback (most recent call last):
    File "/home/fksparv/.pyenv/versions/3.9.0/lib/python3.9/threading.py", line 1486, in _after_fork
      thread._reset_internal_locks(True)
    File "/home/fksparv/.pyenv/versions/3.9.0/lib/python3.9/threading.py", line 829, in _reset_internal_locks
      self._tstate_lock._at_fork_reinit()
  AttributeError: 'NoneType' object has no attribute '_at_fork_reinit'