Description of problem:
try to install to pre-existing LVM vg
The following was filed automatically by anaconda:
anaconda 18.37.11 exception report
Traceback (most recent call first):
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicelibs/lvm.py", line 401, in lvactivate
    raise LVMError("lvactivate failed for %s: %s" % (lv_name, msg))
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devices.py", line 2542, in _setup
    lvm.lvactivate(self.vg.name, self._name)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devices.py", line 714, in setup
    self._setup(orig=orig)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/deviceaction.py", line 492, in execute
    self.device.setup(orig=True)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/devicetree.py", line 323, in processActions
    action.execute()
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 323, in doIt
    self.devicetree.processActions()
  File "/usr/lib64/python2.7/site-packages/pyanaconda/storage/__init__.py", line 174, in turnOnFilesystems
    storage.doIt()
  File "/usr/lib64/python2.7/site-packages/pyanaconda/install.py", line 114, in doInstall
    turnOnFilesystems(storage)
  File "/usr/lib64/python2.7/threading.py", line 504, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/usr/lib64/python2.7/site-packages/pyanaconda/threads.py", line 91, in run
    threading.Thread.run(self, *args, **kwargs)
LVMError: lvactivate failed for root: running lvm lvchange -a y --config  devices { filter=["r|/sdb1$|","r|/sdb2$|","r|/sdb3$|","r|/loop3$|","r|/loop4$|","r|/loop5$|","r|/loop6$|","r|/loop7$|","r|/sdb$|"] }  virt/root failed

Additional info:
cmdline:        /usr/bin/python  /sbin/anaconda
cmdline_file:   BOOT_IMAGE=/images/pxeboot/vmlinuz inst.stage2=hd:LABEL=Fedora\x2018\x20x86_64
executable:     /sbin/anaconda
hashmarkername: anaconda
kernel:         3.6.10-4.fc18.x86_64
other involved packages: 
package:        anaconda-18.37.11
product:        Fedora
release:        Cannot get release name.
type:           libreport
version:        18