rewrite nose-optional-call check, fixes python2.4 compat

--HG--
branch : trunk

_py/test/plugin/pytest_nose.py

@@ -91,9 +91,8 @@ def pytest_make_collect_report(collector):
 def call_optional(obj, name):
     method = getattr(obj, name, None)
     if method:
-        argspec = inspect.getargspec(method)
-        if argspec[0] == ['self']:
-            argspec = argspec[1:]
-        if not any(argspec):
+        ismethod = inspect.ismethod(method)
+        rawcode = py.code.getrawcode(method)
+        if not rawcode.co_varnames[ismethod:]:
             method()
             return True