title: yo @microsoft/sharepoint fails on TypeError: lookups.flatMap is not a function
body: <p>After installation of Node v10.16.1 and installation of gulp and yo (Everything looks alright !) it fails on command <code>yo @microsoft/sharepoint</code>  with TypeError: lookups.flatMap is not a function</p>
  <pre><code>C:\Users\MYNAME\AppData\Roaming\npm\node_modules\yo\node_modules\yeoman-environment\lib\resolver.js:70
      filePatterns: lookups.flatMap(prefix =&gt; [`${prefix}/*/index.ts`, `${prefix}/*/index.js`]),
                            ^
  
  TypeError: lookups.flatMap is not a function
      at Environment.resolver.lookup (C:\Users\MYNAME\AppData\Roaming\npm\node_modules\yo\node_modules\yeoman-environment\lib\resolver.js:70:27)
      at init (C:\Users\MYNAME\AppData\Roaming\npm\node_modules\yo\lib\cli.js:130:7)
      at pre (C:\Users\MYNAME\AppData\Roaming\npm\node_modules\yo\lib\cli.js:89:3)
      at Object.&lt;anonymous&gt; (C:\Users\MYNAME\AppData\Roaming\npm\node_modules\yo\lib\cli.js:219:3)
      at Module._compile (internal/modules/cjs/loader.js:778:30)
      at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
      at Module.load (internal/modules/cjs/loader.js:653:32)
      at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
      at Function.Module._load (internal/modules/cjs/loader.js:585:3)
      at Function.Module.runMain (internal/modules/cjs/loader.js:831:12)
  </code></pre>
  <p>I am a beginner ! Few days ago it worked , then I installed nvm (following a microsoft instruction to swap node v8 to node v10) and then problems started and i uninstalled nvm, node v8 and v10 en reinstalled node v10. The TypeError returns. Perhaps something to do with path ?<br />
  Any idea ? thx</p>