Simplify promises in cli/api.js (#3198)

cli/api.js

@@ -90,40 +90,32 @@ function getPackageName(plugin) {
 
 function install(plugin, locally) {
   const array = locally ? getLocalPlugins() : getPlugins();
-  return new Promise((resolve, reject) => {
+  return existsOnNpm(plugin)
-    existsOnNpm(plugin)
-      .then(() => {
-        if (isInstalled(plugin, locally)) {
-          return reject(`${plugin} is already installed`);
-        }
-
-        array.push(recast.types.builders.literal(plugin));
-        save()
-          .then(resolve)
-          .catch(err => reject(err));
-      })
     .catch(err => {
       const {statusCode} = err;
       if (statusCode && (statusCode === 404 || statusCode === 200)) {
-          return reject(`${plugin} not found on npm`);
+        return Promise.reject(`${plugin} not found on npm`);
       }
-        return reject(`${err.message}\nPlugin check failed. Check your internet connection or retry later.`);
+      return Promise.reject(`${err.message}\nPlugin check failed. Check your internet connection or retry later.`);
-      });
+    })
+    .then(() => {
+      if (isInstalled(plugin, locally)) {
+        return Promise.reject(`${plugin} is already installed`);
+      }
+
+      array.push(recast.types.builders.literal(plugin));
+      return save();
     });
 }
 
 function uninstall(plugin) {
-  return new Promise((resolve, reject) => {
   if (!isInstalled(plugin)) {
-      return reject(`${plugin} is not installed`);
+    return Promise.reject(`${plugin} is not installed`);
   }
 
   const index = getPlugins().findIndex(entry => entry.value === plugin);
   getPlugins().splice(index, 1);
-    save()
+  return save();
-      .then(resolve)
-      .catch(err => reject(err));
-  });
 }
 
 function list() {