Leak pluggin', bug fixin' and better documentin'. Specifically,

module__doc__: Document the Warning subclass heirarchy.

make_class(): Added a "goto finally" so that if populate_methods()
fails, the return status will be -1 (failure) instead of 0 (success).

fini_exceptions(): When decref'ing the static pointers to the
exception classes, clear out their dictionaries too.  This breaks a
cycle from class->dict->method->class and allows the classes with
unbound methods to be reclaimed.  This plugs a large memory leak in a
common Py_Initialize()/dosomething/Py_Finalize() loop.

Python/exceptions.c

@@ -53,51 +53,58 @@ Exception\n\
  |\n\
  +-- SystemExit\n\
  +-- StandardError\n\
+ |    |\n\
+ |    +-- KeyboardInterrupt\n\
+ |    +-- ImportError\n\
+ |    +-- EnvironmentError\n\
+ |    |    |\n\
+ |    |    +-- IOError\n\
+ |    |    +-- OSError\n\
+ |    |         |\n\
+ |    |         +-- WindowsError\n\
+ |    |\n\
+ |    +-- EOFError\n\
+ |    +-- RuntimeError\n\
+ |    |    |\n\
+ |    |    +-- NotImplementedError\n\
+ |    |\n\
+ |    +-- NameError\n\
+ |    |    |\n\
+ |    |    +-- UnboundLocalError\n\
+ |    |\n\
+ |    +-- AttributeError\n\
+ |    +-- SyntaxError\n\
+ |    |    |\n\
+ |    |    +-- IndentationError\n\
+ |    |         |\n\
+ |    |         +-- TabError\n\
+ |    |\n\
+ |    +-- TypeError\n\
+ |    +-- AssertionError\n\
+ |    +-- LookupError\n\
+ |    |    |\n\
+ |    |    +-- IndexError\n\
+ |    |    +-- KeyError\n\
+ |    |\n\
+ |    +-- ArithmeticError\n\
+ |    |    |\n\
+ |    |    +-- OverflowError\n\
+ |    |    +-- ZeroDivisionError\n\
+ |    |    +-- FloatingPointError\n\
+ |    |\n\
+ |    +-- ValueError\n\
+ |    |    |\n\
+ |    |    +-- UnicodeError\n\
+ |    |\n\
+ |    +-- SystemError\n\
+ |    +-- MemoryError\n\
  |\n\
-      +-- KeyboardInterrupt\n\
-      +-- ImportError\n\
-      +-- EnvironmentError\n\
-      |    |\n\
-      |    +-- IOError\n\
-      |    +-- OSError\n\
-      |         |\n\
-      |         +-- WindowsError\n\
+ +---Warning\n\
       |\n\
-      +-- EOFError\n\
-      +-- RuntimeError\n\
-      |    |\n\
-      |    +-- NotImplementedError\n\
-      |\n\
-      +-- NameError\n\
-      |    |\n\
-      |    +-- UnboundLocalError\n\
-      |\n\
-      +-- AttributeError\n\
-      +-- SyntaxError\n\
-      |    |\n\
-      |    +-- IndentationError\n\
-      |         |\n\
-      |         +-- TabError\n\
-      |\n\
-      +-- TypeError\n\
-      +-- AssertionError\n\
-      +-- LookupError\n\
-      |    |\n\
-      |    +-- IndexError\n\
-      |    +-- KeyError\n\
-      |\n\
-      +-- ArithmeticError\n\
-      |    |\n\
-      |    +-- OverflowError\n\
-      |    +-- ZeroDivisionError\n\
-      |    +-- FloatingPointError\n\
-      |\n\
-      +-- ValueError\n\
-      |    |\n\
-      |    +-- UnicodeError\n\
-      |\n\
-      +-- SystemError\n\
-      +-- MemoryError";
+      +-- UserWarning\n\
+      +-- DeprecationWarning\n\
+      +-- SyntaxWarning\n\
+      +-- RuntimeWarning";
 
 
 /* Helper function for populating a dictionary with method wrappers. */
@@ -168,6 +175,7 @@ make_class(PyObject **klass, PyObject *base,
     if (populate_methods(*klass, dict, methods)) {
 	Py_DECREF(*klass);
 	*klass = NULL;
+	goto finally;
     }
 
     status = 0;
@@ -1132,6 +1140,14 @@ fini_exceptions(void)
     PyExc_MemoryErrorInst = NULL;
 
     for (i=0; exctable[i].name; i++) {
+	/* clear the class's dictionary, freeing up circular references
+	 * between the class and its methods.
+	 */
+	PyObject* cdict = PyObject_GetAttrString(*exctable[i].exc, "__dict__");
+	PyDict_Clear(cdict);
+	Py_DECREF(cdict);
+
+	/* Now decref the exception class */
 	Py_XDECREF(*exctable[i].exc);
 	*exctable[i].exc = NULL;
     }