The failing command and error message is:
qemu-img convert -O raw /opt/stack/data/nova/instances/_base/9916110004678060463128e2f14a55ac921f479c.part /opt/stack/data/nova/instances/_base/9916110004678060463128e2f14a55ac921f479c.converted
qemu-img: error while reading sector 941568: Input/output error
This looks to me like the input disk (presumably in qcow2 format) is corrupt.
The failing command and error message is: data/nova/ instances/ _base/991611000 4678060463128e2 f14a55ac921f479 c.part /opt/stack/ data/nova/ instances/ _base/991611000 4678060463128e2 f14a55ac921f479 c.converted
qemu-img convert -O raw /opt/stack/
qemu-img: error while reading sector 941568: Input/output error
This looks to me like the input disk (presumably in qcow2 format) is corrupt.