UnhandledPromiseRejectionWarning: Unhandled promise rejection.

**Description:**

Most of the times, when i am working on ionic app, when ever i make few changes in the code, this is the issue i am getting. It is not even allowing me to work continuously for five minutes. It is totally wasting time. I tried with ionic cli 3.x and then switched to 4.x but still the same issue with both the versions.


**Steps to Reproduce:**

**Output:**

**My `ionic info`:**

```
[WARN] You are not in an Ionic project directory. Project context may be missing.
cli packages: (/xxxxxxxxxxx/node/v8.11.2/lib/node_modules)

@ionic/cli-utils : 2.0.0-alpha.0405736c
ionic (Ionic CLI) : 4.0.0-alpha.0405736c

System:

NodeJS : v8.11.2
npm : 6.0.1
OS : macOS High Sierra
```

**Other Information:**

首先，使用列出的 Node.js、npm 和 macOS 版本，在回報的 Ionic CLI 3.x 和 4.x 環境中編輯 Ionic 應用程式時重現警告。擷取完整的詳細輸出，並找出觸發未處理拒絕的操作；當警告不再中斷持續工作時，即表示完成。

由索引模型根據 Issue 內容生成。