Conditionalize nested test for py2

__qualname__ didn't exist before python 3.3. Skip checks that depend on it if running in earlier Python versions

test/nested.py

@@ -13,7 +13,10 @@
     >>> X.__name__
     'X'
     
-    >>> X.Y
+    >>> X.Y # doctest: +py2
+    <class 'nested_ext.Y'>
+
+    >>> X.Y # doctest: +py3
     <class 'nested_ext.X.Y'>
     
     >>> X.Y.__module__
@@ -22,16 +25,22 @@
     >>> X.Y.__name__
     'Y'
 
-    >>> X.color.__qualname__
+    >>> getattr(X.color, "__qualname__", None) # doctest: +py3
     'X.color'
 
-    >>> repr(X.color.red)
+    >>> repr(X.color.red) # doctest: +py2
+    'nested_ext.color.red'
+
+    >>> repr(X.color.red) # doctest: +py3
     'nested_ext.X.color.red'
 
-    >>> repr(X.color(1))
+    >>> repr(X.color(1)) # doctest: +py2
+    'nested_ext.color(1)'
+
+    >>> repr(X.color(1)) # doctest: +py3
     'nested_ext.X.color(1)'
 
-    >>> test_function.__doc__.strip().split('\\n')[0]
+    >>> test_function.__doc__.strip().split('\\n')[0] # doctest: +py3
     'test_function( (X)arg1, (X.Y)arg2) -> None :'
     
 '''
@@ -42,7 +51,23 @@ def run(args = None):
 
     if args is not None:
         sys.argv = args
-    return doctest.testmod(sys.modules.get(__name__))
+
+    py2 = doctest.register_optionflag("py2")
+    py3 = doctest.register_optionflag("py3")
+
+    class ConditionalChecker(doctest.OutputChecker):
+        def check_output(self, want, got, optionflags):
+            if (optionflags & py3) and (sys.version_info[0] < 3):
+                return True
+            if (optionflags & py2) and (sys.version_info[0] >= 3):
+                return True
+            return doctest.OutputChecker.check_output(self, want, got, optionflags)
+
+    runner = doctest.DocTestRunner(ConditionalChecker())
+    for test in doctest.DocTestFinder().find(sys.modules.get(__name__)):
+        runner.run(test)
+
+    return doctest.TestResults(runner.failures, runner.tries)
 
 if __name__ == '__main__':
     print("running...")