Fix crash in logging checker on a non-UTF-8 bytes format string

doc/whatsnew/fragments/10813.bugfix

@@ -0,0 +1,3 @@
+Fix a crash in the logging checker when a logging call uses a ``bytes`` format string that is not valid UTF-8.
+
+Closes #10813

pylint/checkers/logging.py

@@ -330,7 +330,10 @@ def _check_format_string(self, node: nodes.Call, format_arg: Literal[0, 1]) -> N
         format_string = node.args[format_arg].value
         required_num_args = 0
         if isinstance(format_string, bytes):
-            format_string = format_string.decode()
+            # ``logging`` applies ``str()`` to the message before interpolation,
+            # so mirror that here. ``bytes.decode()`` would raise
+            # ``UnicodeDecodeError`` on non-UTF-8 bytes and crash the checker.
+            format_string = str(format_string)
         if isinstance(format_string, str):
             try:
                 if self._format_style == "old":

tests/functional/l/logging/logging_bytes_format_string.py

@@ -0,0 +1,13 @@
+# pylint: disable=missing-module-docstring
+import logging
+
+# Regression test for https://github.com/pylint-dev/pylint/issues/10813
+# A bytes format string that is not valid UTF-8 used to crash the checker
+# with a ``UnicodeDecodeError``.
+logging.critical(b"\xc0\xc0")
+
+# Valid bytes format strings should still have their arguments checked, as
+# ``logging`` applies ``str()`` to the message before interpolation.
+logging.error(b"%s", "arg")
+logging.error(b"%s")  # [logging-too-few-args]
+logging.error(b"%s", 1, 2)  # [logging-too-many-args]

tests/functional/l/logging/logging_bytes_format_string.txt

@@ -0,0 +1,2 @@
+logging-too-few-args:12:0:12:20::Not enough arguments for logging format string:UNDEFINED
+logging-too-many-args:13:0:13:26::Too many arguments for logging format string:HIGH