Where is util.py

I've just installed PostgresSQL 9.6.11 to test an application. I would
like to run postgres as a service under windows, so I executed
create_service.bat. The new service is listed in windows services but it
doesnt start. The reason is a python error:

> Traceback (most recent call last):
>   File "D:\Programmi\PostgreSQL\9.6\pg96\run-pgctl.py", line 15, in
> <module>
>     import util
> ImportError: No module named util

I seeked for util.py but I couldn't find it. I tried to comment-out
'import util' from run-pgctl.py module, following a suggestion found in
stack overflow, but wasn't effective as the error changed to:

> Traceback (most recent call last):
>   File "D:\Programmi\PostgreSQL\9.6\pg96\run-pgctl.py", line 17, in
> <module>
>     util.set_lang_path()
> NameError: name 'util' is not defined
>
so I restored the 'import util' statement.

How can I solve this problem?
Where should I find util.py?
How can I run postgres service avoiding python?