Mounting loop device fails when creating centos7 image

A simple 'disk-image-create centos7 devuser vm' on current git HEAD d6794ba673acc414c8d15e0d8ac69f27308beb1a gives me the following output

< HTTP/1.1 304 Not Modified
< Date: Tue, 27 Sep 2016 09:33:15 GMT
< Server: Apache/2.4.6 (CentOS)
< ETag: "ed0de14-53bd318eee180"
<
* Curl_http_done: called premature == 0
  0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:-- 0
* Connection #0 to host cloud.centos.org left intact
Server copy has not changed. Using locally cached http://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2.xz
Repacking base image as tarball.
Working in /tmp/tmp.xPrpDUfr2f
/dev/loop1
mount: wrong fs type, bad option, bad superblock on /dev/mapper/loop0p1p1,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
loop deleted : /dev/loop0p1
Unmount /tmp/dib_build.UhK1axov/mnt/tmp/ccache