Disable lib2to3 by default, unless run explicitly.
diff --git a/Lib/test/test_lib2to3.py b/Lib/test/test_lib2to3.py
index 161b9dd..6d589d8 100644
--- a/Lib/test/test_lib2to3.py
+++ b/Lib/test/test_lib2to3.py
@@ -2,7 +2,11 @@
# because of running
from lib2to3.tests import test_fixers, test_pytree, test_util
import unittest
-from test.test_support import run_unittest
+from test.test_support import run_unittest, requires
+
+# Don't run lib2to3 tests by default since they take too long
+if __name__ != '__main__':
+ requires('lib2to3')
def suite():
tests = unittest.TestSuite()