Redirect error output properly during unit testing

Cython/TestUtils.py

@@ -38,6 +38,15 @@ def treetypes(root):
 
 class CythonTest(unittest.TestCase):
 
+    def setUp(self):
+        self.listing_file = Errors.listing_file
+        self.echo_file = Errors.echo_file
+        Errors.listing_file = Errors.echo_file = None
+ 
+    def tearDown(self):
+        Errors.listing_file = self.listing_file
+        Errors.echo_file = self.echo_file
+ 
     def assertLines(self, expected, result):
         "Checks that the given strings or lists of strings are equal line by line"
         if not isinstance(expected, list): expected = expected.split(u"\n")