你fetch的这个地址虽然是https的，但是里面是301跳转，又跳回http了。
[root@localhost ~]# curl https://vanishingdante.github.io/gh-pages-blog-api/2017/02/11/bye-world -i
HTTP/1.1 301 Moved Permanently
Server: GitHub.com
Content-Type: text/html
Location: http://vanishingdante.github.io/gh-pages-blog-api/2017/02/11/bye-world/
Access-Control-Allow-Origin: *
Expires: Mon, 20 Feb 2017 03:31:30 GMT
Cache-Control: max-age=600
X-GitHub-Request-Id: DCFE:28E4:64D5D4E:8722232:58AA60B9
Content-Length: 178
Accept-Ranges: bytes
Date: Mon, 20 Feb 2017 03:21:34 GMT
Via: 1.1 varnish
Age: 4
Connection: keep-alive
X-Served-By: cache-itm7424-ITM
X-Cache: HIT
X-Cache-Hits: 1
X-Timer: S1487560894.032116,VS0,VE0
Vary: Accept-Encoding
X-Fastly-Request-ID: e55e5f1de288a19b7772c1ac3902ce61bd121201
<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<center><h1>301 Moved Permanently</h1></center>
<hr><center>nginx</center>
</body>
</html>
不仅如此，尝试再去请求这个http地址，又会跳转到https：
[root@localhost ~]# curl http://vanishingdante.github.io/gh-pages-blog-api/2017/02/11/bye-world -i
HTTP/1.1 301 Moved Permanently
Server: GitHub.com
Content-Type: text/html
Location: https://vanishingdante.github.io/gh-pages-blog-api/2017/02/11/bye-world
X-GitHub-Request-Id: A1F0:61E6:4D0C0CE:60DEE17:58AA6105
Content-Length: 178
Accept-Ranges: bytes
Date: Mon, 20 Feb 2017 03:22:45 GMT
Via: 1.1 varnish
Age: 0
Connection: keep-alive
X-Served-By: cache-itm7420-ITM
X-Cache: MISS
X-Cache-Hits: 0
X-Timer: S1487560965.336320,VS0,VE191
Vary: Accept-Encoding
X-Fastly-Request-ID: f1d26de898e81b14cf0dacbe28ad6dc716fca747
<html>
<head><title>301 Moved Permanently</title></head>
<body bgcolor="white">
<center><h1>301 Moved Permanently</h1></center>
<hr><center>nginx</center>
</body>
</html>
你的gh-pages有问题。
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