Merge pull request #1070 from reactjs/wtf-netlify-yarn

debug - print yarn version

package.json

@@ -57,7 +57,7 @@
   },
   "engines": {
     "node": "^8.4.0",
-    "yarn": "^1.6.0"
+    "yarn": "^1.3.2"
   },
   "homepage": "https://reactjs.org/",
   "keywords": [
@@ -78,7 +78,7 @@
     "format:source": "prettier --config .prettierrc --write \"{gatsby-*.js,{flow-typed,plugins,src}/**/*.js}\"",
     "format:examples": "prettier --config .prettierrc.examples --write \"examples/**/*.js\"",
     "lint": "eslint .",
-    "netlify": "rimraf node_modules && yarn install --frozen-lockfile --check-files && yarn build",
+    "netlify": "yarn --version && rimraf node_modules && yarn install --frozen-lockfile --check-files && yarn build",
     "nit:source": "prettier --config .prettierrc --list-different \"{gatsby-*.js,{flow-typed,plugins,src}/**/*.js}\"",
     "nit:examples": "prettier --config .prettierrc.examples --list-different \"examples/**/*.js\"",
     "prettier": "yarn format:source && yarn format:examples",