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yarn install v1.3.2
[1/4] Resolving packages...
[2/4] Fetching packages...
info fsevents@1.1.2: The platform "linux" is incompatible with this module.
info "fsevents@1.1.2" is an optional dependency and failed compatibility check. Excluding it from installation.
info fsevents@1.1.3: The platform "linux" is incompatible with this module.
info "fsevents@1.1.3" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
warning "firebase > @firebase/database@0.1.6" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/firestore@0.2.2" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/storage@0.1.5" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/auth > @firebase/auth-types@0.1.0" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/database > @firebase/database-types@0.1.0" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/firestore > @firebase/firestore-types@0.1.0" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/messaging > @firebase/messaging-types@0.1.0" has unmet peer dependency "@firebase/app-types@^0.1.0".
warning "firebase > @firebase/storage > @firebase/storage-types@0.1.0" has unmet peer dependency "@firebase/app-types@^0.1.0".
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In this build on Travis I happened to see these warnings: