added old-style classes regression test

src/allmydata/test/test_python2_regressions.py

@@ -0,0 +1,31 @@
+"""
+Tests to check for Python2 regressions
+"""
+from twisted.trial import unittest
+from twisted.python.modules import getModule
+
+class PythonTwoRegressions(unittest.TestCase):
+    """
+    A test class to hold Python2 regression tests.
+    """
+
+    def is_new_style(self, cls):
+        """check for being a new-style class"""
+        # another test could be: issubclass(value, type)
+        has_class_attr = hasattr(cls, '__class__')
+        dict_or_slots = '__dict__' in dir(cls) or hasattr(cls, '__slots__')
+        return has_class_attr and dict_or_slots
+
+    def test_old_style_class(self):
+        """
+        Check if all classes are new-style classes
+        """
+        for mod in getModule("allmydata").walkModules():
+            for attr in mod.iterAttributes():
+                value = attr.load()
+                if isinstance(value, str):
+                    # apparently strings are note a new-style class (in Python 2.7)
+                    # so we skip testing them
+                    return
+                self.assertTrue(self.is_new_style(value),
+                                "{} does not seem to be a new-style class".format(attr.name))