Caption download from YouTube working

$ ./main.py
Found 6 videos
Found 1 videos with caption tracks
testVideo1 has the following caption tracks
    en: 32 lines, Machine generated = True, written to /tmp/downloaded_subtitles/en_32_True_Ch4LEO3ZhwUaFQjIic2vrcLuxCYSAmVuGgAiA2Fzcgw.srt
    fr: 24 lines, Machine generated = False, written to /tmp/downloaded_subtitles/fr_24_False_ChkLEO3ZhwUaEAjIic2vrcLuxCYSAmZyGgAM.srt
    es-MX: 24 lines, Machine generated = False, written to /tmp/downloaded_subtitles/es-MX_24_False_ChwLEO3ZhwUaEwjIic2vrcLuxCYSBWVzLU1YGgAM.srt
    en: 30 lines, Machine generated = False, written to /tmp/downloaded_subtitles/en_30_False_Ch0LEO3ZhwUaFAjIic2vrcLuxCYSAmVuGgRhdXRvDA.srt
    en: 24 lines, Machine generated = False, written to /tmp/downloaded_subtitles/en_24_False_ChkLEO3ZhwUaEAjIic2vrcLuxCYSAmVuGgAM.srt
    es-ES: 24 lines, Machine generated = False, written to /tmp/downloaded_subtitles/es-ES_24_False_ChwLEO3ZhwUaEwjIic2vrcLuxCYSBWVzLUVTGgAM.srt

Test Plan:
./main.py
.sub to .pot conversion working