avoid importing old assertion interpretation code by default (fixes #537)

CHANGELOG

@@ -1,6 +1,8 @@
 NEXT (2.6)
 -----------------------------------
 
+- fix issue537: Avoid importing old assertion reinterpretation code by default.
+
 - fix issue364: shorten and enhance tracebacks representation by default.  
   The new "--tb=auto" option (default) will only display long tracebacks
   for the first and last entry.  You can get the old behaviour of printing

_pytest/assertion/reinterpret.py

@@ -45,10 +45,8 @@ class AssertionError(BuiltinAssertionError):
 
 if sys.version_info > (3, 0):
     AssertionError.__module__ = "builtins"
-    reinterpret_old = "old reinterpretation not available for py3"
-else:
-    from _pytest.assertion.oldinterpret import interpret as reinterpret_old
+
 if sys.version_info >= (2, 6) or (sys.platform.startswith("java")):
     from _pytest.assertion.newinterpret import interpret as reinterpret
 else:
-    reinterpret = reinterpret_old
+    from _pytest.assertion.oldinterpret import interpret as reinterpret