Does adding something like
before_install:
- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then wget https://launchpad.net/~mc3man/+archive/ubuntu/trusty-media/+files/ffmpeg_3.3.3~trusty2_amd64.deb ; fi
- if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo dpkg -i ffmpeg_3.3.3~trusty2_amd64.deb ; fi
in travis.yml
work?
Note that this is just a guess based on how Plots.jl installs wkhtmltox on travis for the tests. (See https://github.com/JuliaPlots/Plots.jl/blob/master/.travis.yml#L21 and https://github.com/JuliaPlots/Plots.jl/blob/master/test/install_wkhtmltoimage.sh)