fix(yarn): throw errors when registry down

Detect strings in `yarn` `stderr` that indicate a registry problem and if found then throw a `registry-failure` error instead of continuing with a PR creation or update. This way they should be retried on each run until the registry is available again.

Closes #2474, Closes #2475

lib/manager/npm/post-update/yarn.js

@@ -87,9 +87,18 @@ async function generateLockFile(tmpDir, env) {
       },
       'lock file error'
     );
-    if (err.stderr && err.stderr.includes('ENOSPC: no space left on device')) {
+    if (err.stderr) {
+      if (err.stderr.includes('ENOSPC: no space left on device')) {
         throw new Error('Out of disk space when generating yarn.lock');
       }
+      if (
+        err.stderr.includes('The registry may be down.') ||
+        err.stderr.includes('getaddrinfo ENOTFOUND registry.yarnpkg.com') ||
+        err.stderr.includes('getaddrinfo ENOTFOUND registry.npmjs.org')
+      ) {
+        throw new Error('registry-failure');
+      }
+    }
     return { error: true, stderr: err.stderr };
   }
   return { lockFile };