scripts/kernel-doc.py: Properly handle Werror and exit codes

The original kernel-doc script has a logic to return warnings
as errors, and to report the number of warnings found, if in
verbose mode.

Implement it to be fully compatible with the original script.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/de33b0cebd9fdf82d8b221bcfe41db7269286222.1744106242.git.mchehab+huawei@kernel.org

scripts/lib/kdoc/kdoc_files.py

@@ -12,7 +12,6 @@ import argparse
 import logging
 import os
 import re
-import sys
 
 from kdoc_parser import KernelDoc
 from kdoc_output import OutputFormat
@@ -109,7 +108,7 @@ class KernelFiles():
                     KernelDoc.process_export(self.config.function_table, line)
 
         except IOError:
-            print(f"Error: Cannot open fname {fname}", fname=sys.stderr)
+            self.config.log.error("Error: Cannot open fname %s", fname)
             self.config.errors += 1
 
     def file_not_found_cb(self, fname):
@@ -262,3 +261,12 @@ class KernelFiles():
                                             fname, ln, dtype)
             if msg:
                 yield fname, msg
+
+    @property
+    def errors(self):
+        """
+        Return a count of the number of warnings found, including
+        the ones displayed while interacting over self.msg.
+        """
+
+        return self.config.errors