Testing R package on Travis fails because of TeXLive incompatible versions
This issue is due to the CTAN mirrors having yet to update. The issue appears in the Travis R community forum:


  might be related to the recent switch to TexLive-2019 as the LaTeX package manager seems to fail finding inconsolata in the repository.
  
  ...
  
  It looks to me like the mirror chosen was has not updated to 2019, so I think this will resolve itself naturally when the mirrors catch up. If not I can look into it.


In the meantime, I solved it by forcing a previous version of TeXLive with a downgrade to OSX 10.12 in .travis.yml:

# macOS 10.12 version
osx_image: xcode9.2


See this Travis page for the correspondence between XCode and OSX versions.