os-autoinst-4.6-25.20200804gitb781299.fc34 fails to build in Fedora 34:

2: ./18-qemu-options.t ...................... ok
2: 
2: #   Failed test 'init_blockdev_images can report error'
2: #   at ./18-qemu.t line 158.
2: #                   'init_blockdev_images: 'create -f qcow2 raid/hd0 420G' failed after 2 tries: runcmd 'qemu-img create -f qcow2 raid/hd0 420G' failed with exit code 1: 'Formatting 'raid/hd0', fmt=qcow2 cluster_size=65536 compression_type=zlib size=450971566080 lazy_refcounts=off refcount_bits=16
2: # qemu-img: raid/hd0: Could not create file: No such file or directory' at /builddir/build/BUILD/os-autoinst-b781299edace8743b63e826d85c4f7a24ac70817/osutils.pm line 121.
2: # '
2: #     doesn't match '(?^u:failed after 2 tries.*No such.*directory)'
2: # Looks like you failed 1 test of 40.
2: ./18-qemu.t .............................. 
2: Dubious, test returned 1 (wstat 256, 0x100)
2: Failed 1/40 subtests 
[...]
2: Test Summary Report
2: -------------------
2: ./18-qemu.t                            (Wstat: 256 Tests: 40 Failed: 1)
2:   Failed test:  15
2:   Non-zero exit status: 1
2: Files=33, Tests=885, 168 wallclock secs ( 0.56 usr  0.17 sys + 127.53 cusr 17.58 csys = 145.84 CPU)
2: Result: FAIL
2/2 Test #2: test-perl-testsuite ..............***Failed  168.33 sec
The following tests passed:
	test-installed-files
50% tests passed, 1 tests failed out of 2
Total Test time (real) = 168.57 sec
The following tests FAILED:
	  2 - test-perl-testsuite (Failed)
Errors while running CTest
ninja: build stopped: subcommand failed.
RPM build errors:
error: Bad exit status from /var/tmp/rpm-tmp.ugcPdm (%check)
    extra tokens at the end of %endif directive in line 88:  %endif # no_fullstack
    extra tokens at the end of %endif directive in line 134:  %endif # no_fullstack
    Bad exit status from /var/tmp/rpm-tmp.ugcPdm (%check)

A difference between the passing and failing build roots is at <https://koschei.fedoraproject.org/build/8817105>