Description of problem:
1. BIOS boot Fedora-Workstation-Live-x86_64-32-20200221.n.0.iso in a qemu-kvm
2. head to custom partitioning, and start deleting mount points from a previous (failed) installation
Version-Release number of selected component:
The following was filed automatically by anaconda:
anaconda 32.24.1 exception report
Traceback (most recent call first):
File "/usr/lib/python3.8/site-packages/dasbus/client/handler.py", line 496, in _handle_method_error
raise exception from None
File "/usr/lib/python3.8/site-packages/dasbus/client/handler.py", line 474, in _get_method_reply
File "/usr/lib/python3.8/site-packages/dasbus/client/handler.py", line 442, in _call_method
File "/usr/lib64/python3.8/site-packages/pyanaconda/ui/gui/spokes/custom_storage.py", line 1125, in _remove_selected_devices
File "/usr/lib64/python3.8/site-packages/pyanaconda/ui/gui/spokes/custom_storage.py", line 1054, in on_remove_clicked
cmdline: /usr/bin/python3 /sbin/anaconda --liveinst --method=livecd:/dev/mapper/live-base
cmdline_file: BOOT_IMAGE=vmlinuz initrd=initrd.img root=live:CDLABEL=Fedora-WS-Live-32-20200221-n-0 rd.live.image quiet
other involved packages: python3-dasbus-0.2-2.fc32.noarch, anaconda-gui-32.24.1-1.fc32.x86_64
release: Fedora release 32 (Thirty Two)
Created attachment 1665153 [details]
Created attachment 1665154 [details]
Created attachment 1665155 [details]
Created attachment 1665156 [details]
Created attachment 1665157 [details]
Created attachment 1665158 [details]
Created attachment 1665159 [details]
Created attachment 1665160 [details]
Created attachment 1665161 [details]
Created attachment 1665162 [details]
Created attachment 1665163 [details]
This is reproducible, but the exact order matters.
1. custom partitioning
2. under the scheme preset dropdown are two items:
Fedora Linux 32 for x86_64
3. click on unknown to reveal a single mountpoint root/var/lib/machines and delete it
curiously, while that works, "Fedora Linux 32 for x86_64" has vanished, there is still "Unknown"
4. again click on unknown to reveal multiple mountpoints, first one is selected, delete it but first select "delete all file systems which are only used by unknown"
Proposed as a Blocker for 32-beta by Fedora user chrismurphy using the blocker tracking app because:
Beta: Correctly interpret, and modify as described below, any disk with a valid ms-dos or gpt disk label and partition table containing ext4 partitions, LVM and/or btrfs volumes, and/or software RAID arrays at RAID levels 0, 1 and 5 containing ext4 partitions
Fixed in a pull request: https://github.com/rhinstaller/anaconda/pull/2336
Discussed during the 2020-02-24 blocker review meeting: 
The decision to classify this bug as an AcceptedBlocker was made:
"When using both the installer-native and the blivet-gui-based custom partitioning flow, the installer must be able to correctly interpret, and modify any disk with a valid ms-dos or gpt disk label and partition table containing ext4 partitions, LVM and/or btrfs volumes..."
Fixed. Tested both BIOS and UEFI qemu-kvm.
Let's close it, then. Thanks for testing.