check-code: fix class style checking (with tests)

- old-style classes were only checked for one-letter class names
- add check for new-style classes with empty parent class, because
  this is not available in Python 2.4

contrib/check-code.py

@@ -128,7 +128,9 b' pypats = ['
 #    (r'\w*[a-z][A-Z]\w*\s*=', "don't use camelcase in identifiers"),
     (r'^\s*(if|while|def|class|except|try)\s[^[]*:\s*[^\]#\s]+',
      "linebreak after :"),
-    (r'class\s[^(]:', "old-style class, use class foo(object)"),
+    (r'class\s[^( ]+:', "old-style class, use class foo(object)"),
+    (r'class\s[^( ]+\(\):',
+     "class foo() not available in Python 2.4, use class foo(object)"),
     (r'\b(%s)\(' % '|'.join(keyword.kwlist),
      "Python keyword is not a function"),
     (r',]', "unneeded trailing ',' in list"),

tests/test-check-code.t

@@ -27,8 +27,21 b''
   > def any(x):
   >     pass
   > EOF
+  $ cat > classstyle.py <<EOF
+  > class newstyle_class(object):
+  >     pass
+  > 
+  > class oldstyle_class:
+  >     pass
+  > 
+  > class empty():
+  >     pass
+  > 
+  > no_class = 1:
+  >     pass
+  > EOF
   $ check_code="$TESTDIR"/../contrib/check-code.py
-  $ "$check_code" ./wrong.py ./correct.py ./quote.py ./non-py24.py
+  $ "$check_code" ./wrong.py ./correct.py ./quote.py ./non-py24.py ./classstyle.py
   ./wrong.py:1:
    > def toto( arg1, arg2):
    gratuitous whitespace in () or []
@@ -51,6 +64,12 b''
   ./non-py24.py:4:
    >     y = format(x)
    any/all/format not available in Python 2.4
+  ./classstyle.py:4:
+   > class oldstyle_class:
+   old-style class, use class foo(object)
+  ./classstyle.py:7:
+   > class empty():
+   class foo() not available in Python 2.4, use class foo(object)
   [1]
 
   $ cat > is-op.py <<EOF