[nrk] Subtitles can't be converted with python 2.6

[jaimeMF]

For example with http://tv.nrk.no/serie/ikke-gjoer-dette-hjemme/DMPV73000411/sesong-2/episode-1, the problem is that we call xml.etree.ElementTree.Element.itertext in this line, which is not available in 2.6.

We need to call itertext to correctly extract the text from nodes like this one:

<p begin="00:00:36.440" dur="00:00:07.500" style="left">-Vi har sprengt, brent, oversvømt ...<br />-Eksplodert, implodert, kortsluttet.</p>

(Call youtube-dl 'http://tv.nrk.no/serie/ikke-gjoer-dette-hjemme/DMPV73000411/sesong-2/episode-1' --write-sub --sub-format ttml for getting the ttml file)

I haven't looked into the python source code, so I don't know how hard is to backport the function.

[dstftw]

I think it's OK to just workaround this by transform_source.

[jaimeMF]

Thanks for looking into it.