Fix Bug: Cannot get partuuid from loop device

File: lib/disk.py

When installing on a loopback device (a.k.a loop device), function
Filesystem.partuuid_to_index() crashes with a JSON parsing error.

REASON

1) For loop devices, the property BlockDevice.device returns the
   actual image file (back-file) of the loop device instead of the
   /dev/X device.

2) Function Filesystem.partuuid_to_index() executes `lsblk --json`
   against BlockDevice.device .

3) `lsblk` fails and prints the error "not a block device" to stderr.
   This causes the output to not be valid JSON.

4) Code crashes when JSON parser tries to parse the output.

SOLUTION

- Make sure property BlockDevice.device only returns a valid block
  device.

- Create new function BlockDevice.device_or_backfile that mimics
  the present behaviour of BlockDevice.device.

- Use BlockDevice.device_or_backfile in function
  BlockDevice.__repr__().

SOLUTION REASONING

I can only see one reason behind BlockDevice.device returning
the back-file of a loop device, and that is to show the back-file
to the user (instead of /dev/X) when printing the string
representation of a BlockDevice.

All other parts of the code can use the /dev/X file just fine.

And IMO it makes more sense that a property named `device` only
returns devices, and not normal files.

archinstall/lib/disk.py

@@ -244,7 +244,7 @@ class BlockDevice:
 		#       I'm placing the encryption password on a BlockDevice level.
 
 	def __repr__(self, *args, **kwargs):
-		return f"BlockDevice({self.device}, size={self.size}GB, free_space={'+'.join(part[2] for part in self.free_space)}, bus_type={self.bus_type})"
+		return f"BlockDevice({self.device_or_backfile}, size={self.size}GB, free_space={'+'.join(part[2] for part in self.free_space)}, bus_type={self.bus_type})"
 
 	def __iter__(self):
 		for partition in self.partitions:
@@ -285,23 +285,33 @@ class BlockDevice:
 			return device['pttype']
 
 	@property
-	def device(self):
+	def device_or_backfile(self):
 		"""
 		Returns the actual device-endpoint of the BlockDevice.
 		If it's a loop-back-device it returns the back-file,
-		If it's a ATA-drive it returns the /dev/X device
-		And if it's a crypto-device it returns the parent device
+		For other types it return self.device
 		"""
-		if "type" not in self.info:
-			raise DiskError(f'Could not locate backplane info for "{self.path}"')
-
 		if self.info['type'] == 'loop':
 			for drive in json.loads(SysCommand(['losetup', '--json']).decode('UTF_8'))['loopdevices']:
 				if not drive['name'] == self.path:
 					continue
 
 				return drive['back-file']
-		elif self.info['type'] == 'disk':
+		else:
+			return self.device
+
+	@property
+	def device(self):
+		"""
+		Returns the device file of the BlockDevice.
+		If it's a loop-back-device it returns the /dev/X device,
+		If it's a ATA-drive it returns the /dev/X device
+		And if it's a crypto-device it returns the parent device
+		"""
+		if "type" not in self.info:
+			raise DiskError(f'Could not locate backplane info for "{self.path}"')
+
+		if self.info['type'] in ['disk','loop']:
 			return self.path
 		elif self.info['type'][:4] == 'raid':
 			# This should catch /dev/md## raid devices