check-code: allow old style class with special comments

The following chgserver change will use an old style class to comply with
SocketServer's code style. This patch made it possible to pass check-code.

contrib/check-code.py

@@ -245,9 +245,11 b' pypats = ['
      "don't use camelcase in identifiers"),
     (r'^\s*(if|while|def|class|except|try)\s[^[\n]*:\s*[^\\n]#\s]+',
      "linebreak after :"),
-    (r'class\s[^( \n]+:', "old-style class, use class foo(object)"),
+    (r'class\s[^( \n]+:', "old-style class, use class foo(object)",
+     r'#.*old-style'),
     (r'class\s[^( \n]+\(\):',
-     "class foo() creates old style object, use class foo(object)"),
+     "class foo() creates old style object, use class foo(object)",
+     r'#.*old-style'),
     (r'\b(%s)\(' % '|'.join(k for k in keyword.kwlist
                             if k not in ('print', 'exec')),
      "Python keyword is not a function"),