Same here, all my js projects builds are failing. it happens when running jest. 
has there been any update in the images used to build lately?
my travis.yml is basically doing this:
os: osx
language: node_js
node_js:
- node
script:
- yarn test:cov
running test:cov ( test:cov": “jest --coverage && cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js”). Locally will succeed in my case so seems to be really related to the environment on the CI.