fix: update the command use to get package's version using CLI with Y…

…arn 2

Use CLI with Yarn 2 and Node 10 results in an output polluted with:
`(node:87281) ExperimentalWarning: The XXX.promises API is experimental`

These messages are warnings but are send to `stderr` which is causing CLI to throw an error too.
With `sync` function we can check the `status` to know if command ends in error or not and process accordingly.

lib/cli/src/latest_version.js

@@ -122,29 +122,25 @@ function spawnVersionsWithYarn(packageName, constraint) {
  * @param {Object} constraint Version range to use to constraint the returned version
  * @returns {Promise<string|Array<string>>} versions  Promise resolved with a version or an array of versions
  */
-function spawnVersionsWithYarn2(packageName, constraint) {
+async function spawnVersionsWithYarn2(packageName, constraint) {
   const field = constraint ? 'versions' : 'version';
-  return new Promise((resolve, reject) => {
-    const command = spawn('yarn', ['npm', 'info', packageName, '--fields', field, '--json'], {
-      cwd: process.cwd(),
-      env: process.env,
-      stdio: 'pipe',
-      encoding: 'utf-8',
-      silent: true,
-    });
-
-    command.stdout.on('data', (data) => {
-      try {
-        const info = JSON.parse(data);
-        resolve(info[field]);
-      } catch (e) {
-        reject(new Error(`Unable to find versions of ${packageName} using yarn 2`));
-      }
-    });
 
-    command.stderr.on('data', (data) => {
-      const info = JSON.parse(data);
-      reject(new Error(info));
-    });
+  const commandResult = sync('yarn', ['npm', 'info', packageName, '--fields', field, '--json'], {
+    cwd: process.cwd(),
+    env: process.env,
+    stdio: 'pipe',
+    encoding: 'utf-8',
+    silent: true,
   });
+
+  if (commandResult.status !== 0) {
+    throw new Error(commandResult.stderr.toString());
+  }
+
+  try {
+    const parsedOutput = JSON.parse(commandResult.stdout.toString());
+    return parsedOutput[field];
+  } catch (e) {
+    throw new Error(`Unable to find versions of ${packageName} using yarn 2`);
+  }
 }