cleanups requested by @tseaver: remove assert from _implements since …

…all its callers already do this guard; be more explicit about ClassType in test_odd_declarations

src/zope/interface/declarations.py

@@ -436,7 +436,6 @@ def __call__(self, ob):
 def _implements(name, interfaces, classImplements):
     # This entire approach is invalid under Py3K.  Don't even try to fix
     # the coverage for this block there. :(
-    assert not PYTHON3, "Class advice impossible in Python 3"
     frame = sys._getframe(2)
     locals = frame.f_locals
 

src/zope/interface/tests/test_odd_declarations.py

@@ -257,9 +257,12 @@ class C(A, B):
         self.assertEqual(c.c, 1)
         c.c
 
-        import sys
-        if sys.version_info[0] < 3: # This test only makes sense under Python 2.x
+        try:
             from types import ClassType
+        except ImportError:
+            pass
+        else:
+            # This test only makes sense under Python 2.x
             assert not isinstance(C, (type, ClassType))
 
         self.assertIs(C.__class__.__class__, C.__class__)