Modify _fileCopy calling

_fileCopy now returns Promise.

lib/main.js

@@ -492,13 +492,11 @@ Lambda.prototype._archivePrebuilt = function (program, archiveCallback) {
   const codeDirectory = this._codeDirectory()
   const _this = this
 
-  _this._fileCopy(program, program.prebuiltDirectory, codeDirectory, false, (err) => {
-    if (err) {
-      return archiveCallback(err)
-    }
-
+  _this._fileCopy(program, program.prebuiltDirectory, codeDirectory, false).then(() => {
     console.log('=> Zipping deployment package')
     _this._zip(program, codeDirectory).then((data) => archiveCallback(null, data))
+  }).catch((err) => {
+    return archiveCallback(err)
   })
 }
 
@@ -520,29 +518,23 @@ Lambda.prototype._buildAndArchive = function (program, archiveCallback) {
   const codeDirectory = _this._codeDirectory()
   const lambdaSrcDirectory = program.sourceDirectory ? program.sourceDirectory.replace(/\/$/, '') : '.'
 
-  _this._cleanDirectory(codeDirectory).then(() => {
+  return Promise.resolve().then(() => {
+    return _this._cleanDirectory(codeDirectory)
+  }).then(() => {
     console.log('=> Moving files to temporary directory')
-
-    // Move files to tmp folder
-    _this._fileCopy(program, lambdaSrcDirectory, codeDirectory, true, (err) => {
-      if (err) {
-        return archiveCallback(err)
-      }
-
-      console.log('=> Running npm install --production')
-      Promise.resolve().then(() => {
-        return _this._npmInstall(program, codeDirectory)
-      }).then(() => {
-        return _this._postInstallScript(program, codeDirectory)
-      }).then(() => {
-        console.log('=> Zipping deployment package')
-        return _this._zip(program, codeDirectory)
-      }).then((data) => {
-        return archiveCallback(null, data)
-      }).catch((err) => {
-        return archiveCallback(err)
-      })
-    })
+    return _this._fileCopy(program, lambdaSrcDirectory, codeDirectory, true)
+  }).then(() => {
+    console.log('=> Running npm install --production')
+    return _this._npmInstall(program, codeDirectory)
+  }).then(() => {
+    return _this._postInstallScript(program, codeDirectory)
+  }).then(() => {
+    console.log('=> Zipping deployment package')
+    return _this._zip(program, codeDirectory)
+  }).then((data) => {
+    return archiveCallback(null, data)
+  }).catch((err) => {
+    return archiveCallback(err)
   }).catch((err) => {
     return archiveCallback(err)
   })