Problem downloading subtitles on some courses

[xsirvent]

Hi,

Describe the bug
I tried to download some courses with English subtitles only, but instead of downloading .en.srt files, I've got all other languages but English one, like .es.srt, .fr.srt, .pt.srt, .de.srt, etc...

I've already downloaded these courses in the past with an older version of udemy-dl and the English subtitles was downloaded too.

To Reproduce
udemy course url: http://www.udemy.com/the-complete-nodejs-developer-course-2
udemy course url: http://www.udemy.com/bootsrap-4-bootcamp

The command I used is the following (I'm on windows 10 with 'Hyper' terminal
python udemy-dl.py -u USER -p PASS -o FOLDER -q 720 -s en https://sdsglobal.udemy.com/course/the-complete-nodejs-developer-course-2
python udemy-dl.py -u USER -p PASS -o FOLDER -q 720 -s en https://sdsglobal.udemy.com/course/bootstrap-4-bootcamp

Expected behavior
Having English subtitles downloaded.

Screenshots

Python Environment (please complete the following information):

• OS Platform:Windows 10
• Python Version 3.8.5