Description of problem:
Not sure exactly what has changed during an update, because the nosync option had worked previously on this machine, so disabed it, and it could continue.
 maybe something to do with it running an nspawn chroot ?

Version-Release number of selected component:
mock-1.2.14-1.fc23

Additional info:
reporter:       libreport-2.6.3
cmdline:        /usr/bin/python3 -tt /sbin/mock --dnf --update --buildsrpm --spec=zsh.spec --sources=.
executable:     /sbin/mock
kernel:         4.2.8-300.fc23.x86_64
runlevel:       N 5
type:           Python3
uid:            1000

Truncated backtrace:
shutil.py:420:_rmtree_safe_fd:PermissionError: [Errno 13] Permission denied: 'nosync.so'

Traceback (most recent call last):
  File "/sbin/mock", line 649, in main
    run_command(options, args, config_opts, commands, buildroot, state)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/sbin/mock", line 732, in run_command
    do_buildsrpm(config_opts, commands, buildroot, options, args)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/sbin/mock", line 511, in do_buildsrpm
    cmd=cmd, post=None, clean=clean)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/sbin/mock", line 440, in rebuild_generic
    ret = cmd(item)
  File "/sbin/mock", line 509, in cmd
    follow_links=options.symlink_dereference)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/usr/lib/python3.4/site-packages/mockbuild/backend.py", line 335, in buildsrpm
    rebuilt_srpm = self.rebuild_installed_srpm(chrootspec, timeout)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/usr/lib/python3.4/site-packages/mockbuild/backend.py", line 403, in rebuild_installed_srpm
    printOutput=self.config['print_main_output'])
  File "/usr/lib/python3.4/site-packages/mockbuild/buildroot.py", line 184, in doChroot
    env=env, shell=shell, *args, **kargs)
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/usr/lib/python3.4/site-packages/mockbuild/util.py", line 526, in do
    raise exception.Error("Command failed. See logs for output.\n # %s" % (command,), child.returncode)
mockbuild.exception.Error: Command failed. See logs for output.
 # /usr/bin/systemd-nspawn -q -M 4c7778b242804d79beb3d5c72146cf0e -D /var/lib/mock/fedora-23-x86_64/root /bin/su -l mockbuild -c /usr/bin/rpmbuild -bs --target x86_64 --nodeps /builddir/build/SPECS/zsh.spec

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/sbin/mock", line 833, in <module>
    main()
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/sbin/mock", line 651, in main
    buildroot.finalize()
  File "/usr/lib/python3.4/site-packages/mockbuild/trace_decorator.py", line 84, in trace
    result = func(*args, **kw)
  File "/usr/lib/python3.4/site-packages/mockbuild/buildroot.py", line 538, in finalize
    shutil.rmtree(d)
  File "/usr/lib64/python3.4/shutil.py", line 464, in rmtree
    _rmtree_safe_fd(fd, path, onerror)
  File "/usr/lib64/python3.4/shutil.py", line 402, in _rmtree_safe_fd
    _rmtree_safe_fd(dirfd, fullname, onerror)
  File "/usr/lib64/python3.4/shutil.py", line 422, in _rmtree_safe_fd
    onerror(os.unlink, fullname, sys.exc_info())
  File "/usr/lib64/python3.4/shutil.py", line 420, in _rmtree_safe_fd
    os.unlink(name, dir_fd=topfd)
PermissionError: [Errno 13] Permission denied: 'nosync.so'

Local variables in innermost frame:
name: 'nosync.so'
orig_st: os.stat_result(st_mode=33261, st_ino=30455027, st_dev=41, st_nlink=1, st_uid=0, st_gid=0, st_size=7024, st_atime=1451419614, st_mtime=1434583764, st_ctime=1451419614)
mode: 33261
fullname: '/tmp/tmpf_gyasnz/lib64/nosync.so'
onerror: <function rmtree.<locals>.onerror at 0x7f729c131620>
names: ['nosync.so']
path: '/tmp/tmpf_gyasnz/lib64'
topfd: 12