PA4v3 - Backup don't start because of Python 2.7 DLL is missing

Hello!

I set everything as in PA3 or in PA4prevver, but when I try to backup the
DB, I got:

---------------------------
pythonw.exe - Rendszerhiba
---------------------------
Nem folytatható a kód végrehajtása, mert nem található a(z) python27.dll.
...

System error
Cannot continue the execution of the code because python27.dll is missing.

The PG4 is working, only this function not.
I can't see anything in PgAdmin4.log which relates this error.
How can I fix this?
I have installed Python 3.0 in my machine (Windows 10).

---------------
*Version*
3.0
*Copyright*
Copyright 2013 - 2018, The pgAdmin Development Team
*Python Version*
2.7.13 (v2.7.13:a06454b1afa1, Dec 17 2016, 20:42:59) [MSC v.1500 32 bit
(Intel)]
*Flask Version*
0.12.2
*Application Mode*
Desktop
*Current User*
pgadmin4(at)pgadmin(dot)org
---------------

Thanks
dd