diff --git a/tests/run-tests.py b/tests/run-tests.py
--- a/tests/run-tests.py
+++ b/tests/run-tests.py
@@ -1989,7 +1989,10 @@ class TestRunner(object):
         else:
             f = open(installerrs, 'rb')
             for line in f:
-                sys.stdout.write(line)
+                if sys.version_info[0] > 2:
+                    sys.stdout.buffer.write(line)
+                else:
+                    sys.stdout.write(line)
             f.close()
             sys.exit(1)
         os.chdir(self._testdir)