Failure during error reporting in test runner script

[ianfixes]

Error seen here: https://github.com/RobTillaart/SHT31/runs/1479583778?check_suite_focus=true#step:4:25

Requested unittest platform 'leonardo' is defined in 'platforms' YML...        ✓
Library conforms to Arduino library specification...                         1.0
Skipping unit tests; no tests dir at /github/home/Arduino/libraries/SHT31/test... 
  In case that's an error, this is what was found in the library:
bundler: failed to load command: /action/bundle/ruby/2.6.0/bin/arduino_ci.rb (/action/bundle/ruby/2.6.0/bin/arduino_ci.rb)
NameError: uninitialized constant Host
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:160:in `display_files'
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:237:in `block in perform_unit_tests'
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:97:in `perform_action'
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:136:in `inform_multiline'
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:235:in `perform_unit_tests'
  /action/bundle/ruby/2.6.0/bundler/gems/arduino_ci-5ab072c61308/exe/arduino_ci.rb:397:in `<top (required)>'
  /action/bundle/ruby/2.6.0/bin/arduino_ci.rb:23:in `load'
  /action/bundle/ruby/2.6.0/bin/arduino_ci.rb:23:in `<top (required)>'