### Description

I have defined custom maintenance pages for 40x and 50x errors. Currently the html for both has arabic text. Locally through vsCode, I can see the text correctly. Also pasting the html code to the browser does display everything just fine. Except when deploying live, all arabic characters get turned into question marks.

### Steps to reproduce

```
files:
"/usr/share/nginx/html/40x.html" :
mode: "000755"
owner: nginx
group: nginx
content: |



الموقع في حالة صيانة

body { text-align: center; padding: 10%; font: 20px Helvetica, sans-serif; color: #333; }
h1 { font-size: 50px; margin: 0; }
article { display: block; text-align: right; max-width: 650px; margin: 0 auto; }
a { color: #dc8100; text-decoration: none; }
a:hover { color: #333; text-decoration: none; }
@media only screen and (max-width : 480px) {
h1 { font-size: 40px; }
}

لم نتمكن من العثور على تلك الصفحة.

الصفحة التي تبحث عنها بعيدة عن متناولنا

```

### Observed result

deployment works fine. But the produced html files are faulty.

### Expected result

I should see the same text I see on vsCode, but live.

### Additional environment details (Ex: Windows, Mac, Amazon Linux etc)

1. OS: Ubuntu 18.04
2. EBCLI version: 3.19.4 (Python 3.6.9)

Start by reproducing the issue with the shown 40x.html and 50x.html custom file content, then trace how the EB CLI processes the files mapping and writes deployed HTML. Compare the generated files with the source encoding; done means Arabic characters remain intact in the live maintenance pages.

Written by the indexing model from the issue text.