tmdb3/lookup.py - Fail with an exit code if we didn't get any results.

[BobEntwhistle]

Fixes this exception:

/usr/share/mythtv/metadata/Television/tmdb3tv.py -l en -a US -N 2008\ Star\ Wars
Traceback (most recent call last):
  File "/usr/share/mythtv/metadata/Television/tmdb3tv.py", line 159, in <module>
    sys.exit(main("television",'tmdb3tv.py'))
             ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/share/mythtv/metadata/Television/tmdb3tv.py", line 133, in main
    xml = buildEpisode(args[0:2], opts)
  File "/usr/lib/python3/dist-packages/MythTV/tmdb3/lookup.py", line 334, in buildEpisode
    series = results[0]
             ~~~~~~~^^^
  File "/usr/lib/python3/dist-packages/MythTV/tmdb3/pager.py", line 67, in __getitem__
    raise IndexError("list index outside range")
IndexError: list index outside range

Checklist

• contribution does not duplicate one of our existing pull requests
• contribution is in a branch rebased against master
• code compiles successfully without errors
• code follows the MythTV Coding Standards
• documentation added/updated/removed where necessary
• commits are logically organised and have good commit messages