webvtt errors

[gumaerc]

This may be an issue with the source data, but in recent full conversion runs of all courses I have seen a number of SRT -> VTT conversion errors like this:

webvtt.errors.MalformedFileError: The file does not have a valid format.
This file is malformed and cannot be converted to vtt 7.012-2004-L09.srt. The file does not have a valid format.
Traceback (most recent call last):
  File "/home/gumaerc/Code/ocw-data-parser/ocw_data_parser/utils.py", line 317, in convert_to_vtt
    webvtt.from_srt(Path(temp_dir) / "data").save()
  File "/home/gumaerc/.cache/pypoetry/virtualenvs/ocw-data-parser-0hl9ca1d-py3.9/lib/python3.9/site-packages/webvtt/webvtt.py", line 48, in from_srt
    parser = SRTParser().read(file)
  File "/home/gumaerc/.cache/pypoetry/virtualenvs/ocw-data-parser-0hl9ca1d-py3.9/lib/python3.9/site-packages/webvtt/parsers.py", line 25, in read
    self._validate(content)
  File "/home/gumaerc/.cache/pypoetry/virtualenvs/ocw-data-parser-0hl9ca1d-py3.9/lib/python3.9/site-packages/webvtt/parsers.py", line 144, in _validate
    raise MalformedFileError('The file does not have a valid format.')

We should do a cursory investigation of some of the files throwing these errors and see if the issue is actually malformed SRT files or if there is something else causing the issue.