Humanize no video codec error

[red-0ne]

Translate "no video track found in file" errors to errInvalidVideo

[codecov]

Codecov Report

Merging #122 (4e32c53) into main (7438da0) will increase coverage by 0.14621%.
The diff coverage is 100.00000%.

@@                Coverage Diff                @@
##               main       #122         +/-   ##
=================================================
+ Coverage   9.62217%   9.76838%   +0.14621%     
=================================================
  Files            14         14                 
  Lines          1985       1986          +1     
=================================================
+ Hits            191        194          +3     
- Misses         1778       1779          +1     
+ Partials         16         13          -3     

Impacted Files	Coverage Δ
task/runner.go	16.54676% <100.00000%> (+0.68138%)	⬆️

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Impacted Files	Coverage Δ
task/runner.go	16.54676% <100.00000%> (+0.68138%)	⬆️

[victorges]

LGTM but might be worth considering a custom error message in this case since it's so clear anyway. The other invalid video errors we have today we'd actually want to eventually parse the wrong thing (like "invalid video codec: x") then makes sense to keep it simple for now.

I'm fine with it as is anyway though. Might be worth checking if that's enough from the product perspective as well.