Can't run Mentalist

[Czechball]

When I try to run Mentalist (from the releases), I get these errors:

Traceback (most recent call last):
File "pyinstaller_stub.py", line 1, in
File "", line 968, in _find_and_load
File "", line 957, in _find_and_load_unlocked
File "", line 673, in _load_unlocked
File "/usr/local/lib/python3.5/dist-packages/PyInstaller/loader/pyimod03_importers.py", line 631, in exec_module
File "mentalist/controller.py", line 20, in
File "", line 968, in _find_and_load
File "", line 957, in _find_and_load_unlocked
File "", line 673, in _load_unlocked
File "/usr/local/lib/python3.5/dist-packages/PyInstaller/loader/pyimod03_importers.py", line 631, in exec_module
File "mentalist/view/init.py", line 1, in
File "", line 968, in _find_and_load
File "", line 957, in _find_and_load_unlocked
File "", line 673, in _load_unlocked
File "/usr/local/lib/python3.5/dist-packages/PyInstaller/loader/pyimod03_importers.py", line 631, in exec_module
File "mentalist/view/adder.py", line 7, in
File "", line 968, in _find_and_load
File "", line 957, in _find_and_load_unlocked
File "", line 673, in _load_unlocked
File "/usr/local/lib/python3.5/dist-packages/PyInstaller/loader/pyimod03_importers.py", line 631, in exec_module
File "mentalist/view/base_words.py", line 8, in
File "", line 968, in _find_and_load
File "", line 957, in _find_and_load_unlocked
File "", line 673, in _load_unlocked
File "/usr/local/lib/python3.5/dist-packages/PyInstaller/loader/pyimod03_importers.py", line 631, in exec_module
File "mentalist/view/main.py", line 15, in
File "/usr/lib/python3.5/locale.py", line 594, in setlocale
return _setlocale(category, locale)
locale.Error: unsupported locale setting
[2134] Failed to execute script pyinstaller_stub

Any ideas what could be wrong?