download react-is from npm manually

package.json

@@ -70,6 +70,7 @@
     "mkdirp": "^0.5.1",
     "ncp": "^2.0.0",
     "object-assign": "^4.1.1",
+    "pacote": "^9.5.6",
     "prettier": "1.13.7",
     "prop-types": "^15.6.2",
     "random-seed": "^0.3.0",
@@ -100,7 +101,7 @@
     "lint": "node ./scripts/tasks/eslint.js",
     "lint-build": "node ./scripts/rollup/validate/index.js",
     "extract-errors": "yarn build --type=dev --extract-errors",
-    "postinstall": "node node_modules/fbjs-scripts/node/check-dev-engines.js package.json && node ./scripts/flow/createFlowConfigs.js",
+    "postinstall": "node node_modules/fbjs-scripts/node/check-dev-engines.js package.json && node ./scripts/flow/createFlowConfigs.js && node ./scripts/yarn/downloadReactIsForPrettyFormat.js",
     "debug-test": "cross-env NODE_ENV=development node --inspect-brk node_modules/.bin/jest --config ./scripts/jest/config.source.js --runInBand",
     "test": "cross-env NODE_ENV=development jest --config ./scripts/jest/config.source.js",
     "test-persistent": "cross-env NODE_ENV=development jest --config ./scripts/jest/config.source-persistent.js",

scripts/yarn/downloadReactIsForPrettyFormat.js

@@ -0,0 +1,30 @@
+'use strict';
+
+const path = require('path');
+const pacote = require('pacote');
+const rimraf = require('rimraf');
+const prettyFormatPkg = require('pretty-format/package.json');
+const prettyFormatPkgPath = require.resolve('pretty-format/package.json');
+
+const reactIsDependencyVersion = prettyFormatPkg.dependencies['react-is'];
+
+if (!reactIsDependencyVersion) {
+  throw new Error('Unable to find `react-is` dependency in `pretty-format`');
+}
+
+const prettyFormatNodeModulesReactIsDir = path.join(
+  path.dirname(prettyFormatPkgPath),
+  'node_modules/react-is'
+);
+
+rimraf.sync(prettyFormatNodeModulesReactIsDir);
+
+pacote
+  .extract(
+    `react-is@${reactIsDependencyVersion}`,
+    prettyFormatNodeModulesReactIsDir
+  )
+  .catch(error => {
+    console.error(error);
+    process.exitCode = 1;
+  });