disappearing non-ascii symbols in filename when launched by cgi-script of apache

[Sorseg]

python /media/storage/dev/youtube/youtubedl.py -c -v --no-mtime -o %(id)s=%(title)s.%(ext)s http://www.youtube.com/watch?v=fijMt9I5NHM

When I launch this line from console or from python script even when logged in by user www-data everything works ok, but when this line is launched inside script, which is invoked by cgi-script, the youtubedl.py replaces cyrillic letters in the name of output file with random number of spaces. What can be the cause?

code:

import subprocess as sp
ydl = "python /media/storage/dev/youtube/youtubedl.py -c -v --no-mtime -o %(id)s=%(title)s.%(ext)s"
dwnl = sp.Popen(ydl.split()+[url], stdout = sp.PIPE)

[Sorseg]

And no error/warnings in stderr

[Sorseg]

I decided to make sure this is not an apache mod_cgi bug first

[Sorseg]

If I do in same script

with open(u'/media/storage/youtube/downloaded/проверка'.encode('utf8'),'a') as ff:
   ff.write("asdfasdf")

it works fine, the file is created