INFO buildroot.py:317:  Mock Version: 1.3.3
DEBUG util.py:105:  ensuring that dir exists: /var/lib/mock/centos-7-exp-x86_64/root/dev/pts
DEBUG util.py:108:  creating dir: /var/lib/mock/centos-7-exp-x86_64/root/dev/pts
DEBUG util.py:105:  ensuring that dir exists: /var/lib/mock/centos-7-exp-x86_64/root/dev/shm
DEBUG util.py:108:  creating dir: /var/lib/mock/centos-7-exp-x86_64/root/dev/shm
DEBUG buildroot.py:448:  kernel version == 3.10.0-514.10.2.el7.x86_64
DEBUG util.py:118:  touching file: /var/lib/mock/centos-7-exp-x86_64/root/etc/fstab
DEBUG util.py:118:  touching file: /var/lib/mock/centos-7-exp-x86_64/root/etc/yum.conf
DEBUG util.py:118:  touching file: /var/lib/mock/centos-7-exp-x86_64/root/etc/dnf.conf
DEBUG util.py:118:  touching file: /var/lib/mock/centos-7-exp-x86_64/root/var/log/yum.log
DEBUG util.py:184:  kill orphans
DEBUG util.py:594:  child environment: None
DEBUG util.py:518:  Executing command: ['btrfs', 'subv', 'list', '/var/lib/mock'] with env {'LANG': 'en_US.utf8', 'TERM': 'vt100', 'SHELL': '/bin/sh', 'HOSTNAME': 'mock', 'HOME': '/builddir', 'PATH': '/usr/bin:/bin:/usr/sbin:/sbin'} and shell False
DEBUG util.py:573:  Child return code was: 1
DEBUG util.py:1244:  Please ignore the error above above about btrfs.