/perword issue

[sevilaybayatli]

hi,
I followed the instructions in this site to install and work with apertium-apy :http://wiki.apertium.org/wiki/Apertium-apy

sevilay@sevilay-linux:~/engine-code/apertium-apy$ ./servlet.py -p 8080 /home/sevilay/engine-code/
[W 180617 15:57:19 apy:324] Unable to import CLD2, continuing using naive method of language detection
[I 180617 15:57:19 apy:117] 3 generator modes found
[I 180617 15:57:19 apy:117] 1 tokenise modes found
[I 180617 15:57:19 apy:117] 1 spell modes found
[I 180617 15:57:19 apy:117] 2 pair modes found
[I 180617 15:57:19 apy:117] 4 analyzer modes found
[I 180617 15:57:19 apy:117] 4 tagger modes found
[I 180617 15:57:19 apy:348] Serving at http://localhost:8080
[I 180617 15:57:19 systemd:116] No notification socket, not launched via systemd?

all commands worked without any error for example:

curl 'http://localhost:8080/translate?langpair=kaz|tur&q=Сен+бардың+ба?'
{"responseDetails": null, "responseData": {"translatedText": "Sen gittin m\u0131?"}, "responseStatus": 200}sevilay@sevilay-linux:~/engine-code/apertium-apy$

but when I try command of /perword I get this error for example:
curl 'http://localhost:8080/perWord?lang=kaz-tur&modes=morph+biltrans&q=Сен+бардың+ба?'

Error:

Exception in thread Thread-4:
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
File "/usr/lib/python3.5/multiprocessing/pool.py", line 119, in worker
result = (True, func(*args, **kwds))
File "/home/sevilay/engine-code/apertium-apy/apertium_apy/handlers/per_word.py", line 36, in process_per_word
morph_lexical_units = remove_dot_from_deformat(query, re.findall(lexical_unit_re, analysis))
File "/usr/lib/python3.5/re.py", line 213, in findall
return _compile(pattern, flags).findall(string)
TypeError: expected string or bytes-like object
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/lib/python3.5/threading.py", line 914, in _bootstrap_inner
self.run()
File "/usr/lib/python3.5/threading.py", line 862, in run
self._target(*self._args, **self._kwargs)
File "/home/sevilay/engine-code/apertium-apy/apertium_apy/handlers/per_word.py", line 141, in worker
callback(result.get(timeout=self.timeout))
File "/usr/lib/python3.5/multiprocessing/pool.py", line 608, in get
raise self._value
TypeError: expected string or bytes-like object

please can you help me to solve this problem ?