Improve deploy process with Promise

lib/main.js

@@ -805,35 +805,7 @@ Lambda.prototype._deployToRegion = function (program, params, region) {
     // Checking function
     return lambda.getFunction({
       'FunctionName': params.FunctionName
-    }, (err) => {
-      if (err) {
-        // Function does not exist
-        return _this._uploadNew(lambda, params).then((results) => {
-          console.log('=> Zip file(s) done uploading. Results follow: ')
-          console.log(results)
-
-          return Promise.all([
-            _this._updateEventSources(
-              lambda,
-              params.FunctionName,
-              [],
-              eventSourceList.EventSourceMappings
-            ),
-            _this._updateScheduleEvents(
-              scheduleEvents,
-              results.FunctionArn,
-              eventSourceList.ScheduleEvents
-            )
-          ]).then((results) => {
-            resolve(results)
-          }).catch((err) => {
-            reject(err)
-          })
-        }).catch((err) => {
-          reject(err)
-        })
-      }
-
+    }).promise().then(() => {
       // Function exists
       _this._listEventSourceMappings(lambda, {
         'FunctionName': params.FunctionName
@@ -862,6 +834,32 @@ Lambda.prototype._deployToRegion = function (program, params, region) {
           reject(err)
         })
       })
+    }).catch(() => {
+      // Function does not exist
+      return _this._uploadNew(lambda, params).then((results) => {
+        console.log('=> Zip file(s) done uploading. Results follow: ')
+        console.log(results)
+
+        return Promise.all([
+          _this._updateEventSources(
+            lambda,
+            params.FunctionName,
+            [],
+            eventSourceList.EventSourceMappings
+          ),
+          _this._updateScheduleEvents(
+            scheduleEvents,
+            results.FunctionArn,
+            eventSourceList.ScheduleEvents
+          )
+        ]).then((results) => {
+          resolve(results)
+        }).catch((err) => {
+          reject(err)
+        })
+      }).catch((err) => {
+        reject(err)
+      })
     })
   })
 }