file output failure results in UnreadableValue

volatility3/framework/plugins/linux/graphics/fbdev.py

@@ -8,7 +8,12 @@ from dataclasses import dataclass
 from typing import Type, List, Dict, Tuple
 from volatility3.framework import constants, exceptions, interfaces
 from volatility3.framework.configuration import requirements
-from volatility3.framework.renderers import format_hints, TreeGrid, NotAvailableValue
+from volatility3.framework.renderers import (
+    format_hints,
+    TreeGrid,
+    NotAvailableValue,
+    UnreadableValue,
+)
 from volatility3.framework.objects import utility
 from volatility3.framework.constants import architectures
 from volatility3.framework.symbols import linux
@@ -280,11 +285,12 @@ You can try using ffmpeg to decode the raw buffer. Example usage:
                     file_output = self.dump_fb(
                         self.context, kernel_name, self.open, fb, bool(fb.color_fields)
                     )
+                    file_output = str(file_output)
                 except exceptions.InvalidAddressException as excp:
                     vollog.error(
                         f'Layer {excp.layer_name} failed to read address {hex(excp.invalid_address)} when dumping framebuffer "{fb.id}".'
                     )
-                    file_output = "Error"
+                    file_output = UnreadableValue()
 
             try:
                 fb_device_name = utility.pointer_to_string(
@@ -303,7 +309,7 @@ You can try using ffmpeg to decode the raw buffer. Example usage:
                     f"{fb.xres_virtual}x{fb.yres_virtual}",
                     fb.bpp,
                     "RUNNING" if fb.fb_info.state == 0 else "SUSPENDED",
-                    str(file_output),
+                    file_output,
                 ),
             )