Why Red Hat Enterprise Linux 7 install fails on IBM System Z with the error "UnknownSwapError" ?

Issue

• Why Red Hat Enterprise Linux 7 install fails on IBM System Z with the error "UnknownSwapError" ?
• Red Hat Enterprise Linux 7 generates the following backtrace and the install hangs. This only happens when swapgen vdisk is used

anaconda 21.48.22.56-1 exception report
Traceback (most recent call first):
  File "/usr/lib/python2.7/site-packages/blivet/devicelibs/swap.py", line 80, in swapon
    raise UnknownSwapError
  File "/usr/lib/python2.7/site-packages/blivet/formats/swap.py", line 164, in setup
    swap.swapon(self.device, priority=self.priority)
  File "/usr/lib/python2.7/site-packages/blivet/__init__.py", line 2577, in turnOnSwap
    device.format.setup()
  File "/usr/lib/python2.7/site-packages/blivet/__init__.py", line 1617, in turnOnSwap
    self.fsset.turnOnSwap(rootPath=_sysroot)
  File "/usr/lib/python2.7/site-packages/blivet/__init__.py", line 231, in turnOnFilesystems
    storage.turnOnSwap()
  File "/usr/lib64/python2.7/site-packages/pyanaconda/install.py", line 186, in doInstall
    turnOnFilesystems(storage, mountOnly=flags.flags.dirInstall, callbacks=callbacks_reg)
  File "/usr/lib64/python2.7/threading.py", line 764, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/threads.py", line 227, in run
    threading.Thread.run(self, *args, **kwargs)
UnknownSwapError

Local variables in innermost frame:
pagesize: 4096
priority: None
num: 4096
sig: ^@^@^@^@^@^@^@^@^@^@
device: /dev/dasde1
fd: 23
OMITTED BINARY DATA