PathSanitizingFileCheck: improve Python3 compatibility

utils/PathSanitizingFileCheck

@@ -67,20 +67,21 @@ constants.""")
 
     if args.enable_windows_compatibility:
         if args.enable_yaml_compatibility:
-            slashes_re = b'(/|\\\\\\\\|\\\\\\\\\\\\\\\\)'
+            slashes_re = r'(/|\\\\|\\\\\\\\)'
         else:
-            slashes_re = b'(/|\\\\\\\\)'
+            slashes_re = r'(/|\\\\)'
     else:
-        slashes_re = b'/'
+        slashes_re = r'/'
 
-    stdin = io.open(sys.stdin.fileno(), 'rb').read()
+    stdin = io.open(sys.stdin.fileno(), 'r', encoding='utf-8', errors='ignore').read()
 
     for s in args.sanitize_strings:
-        replacement, pattern = s.encode(encoding="utf-8").split(b'=', 1)
+        replacement, pattern = s.split('=', 1)
         # Since we want to use pattern as a regex in some platforms, we need
         # to escape it first, and then replace the escaped slash
         # literal (r'\\/') for our platform-dependent slash regex.
-        stdin = re.sub(re.sub(b'\\\\/', slashes_re, re.escape(pattern)),
+        stdin = re.sub(re.sub('\\\\/' if sys.version_info[0] < 3 else r'[/\\]',
+                              slashes_re, re.escape(pattern)),
                        replacement,
                        stdin)
 
@@ -90,7 +91,7 @@ constants.""")
     else:
         p = subprocess.Popen(
             [args.file_check_path] + unknown_args, stdin=subprocess.PIPE)
-        stdout, stderr = p.communicate(stdin)
+        stdout, stderr = p.communicate(stdin.encode('utf-8'))
         if stdout is not None:
             print(stdout)
         if stderr is not None: