Couldn't resolve host

gitlab-ci-multi-runner 0.7.1 (ee7a001)
Using Docker executor with image ruby:2.1 ...
Pulling docker image gitlab/gitlab-runner:cache ...
Pulling docker image gitlab/gitlab-runner:build ...
Pulling docker image ruby:2.1 ...

Running on runner-c749a15a-project-2-concurrent-0 via myhost...
Cloning repository...
Cloning into '/builds/user/test'...
fatal: unable to access 'http://gitlab-ci-token:xxxxxx@myhost/user/test.git/': Couldn't resolve host 'myhost'

ERROR: Build failed with: exit code 1

However, curl --verbose http://myhost/ gives

* Hostname was NOT found in DNS cache
*   Trying 127.0.1.1...
* Connected to myhost (127.0.1.1) port 80 (#0)
> GET / HTTP/1.1
> User-Agent: curl/7.35.0
> Host: myhost
> Accept: */*
> 
< HTTP/1.1 302 Found

So it finds the host. Is there any way to debug the gitlab-runner.