Why is my .travis.yml file being ignored?

Here is my .travis.yml file:

language: node_js
node_js:
  - "6.10"
  - "6"
cache:
  directories:
    - node_modules

(It is also available on Github.)

Here is my build log on Travis, showing the wrong Node version:

And here is the versionless config for the same build:

Finally, here is the caching report for my build:

I have tried changing my .travis.yml file in numerous ways, including:

• other version strings,
• different indentations and line ending combinations,
• with and without cache, etc.,

but nothing I do seems to have any effect.

I have enabled "Build only if .travis.yml is present", so apparently it is finding the file itself, just not what's in it. What am I missing?

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