make consulting save_modules O(1) rather than O(n)

diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 0007da64b8861df186e21dd0ce61ba1ea0940e29..5239d5a24674285ad3203192e7e1bc9304512a53 100755 (executable)
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -462,7 +462,7 @@ def main(tests=None, testdir=None, verbose=0, quiet=False,
 
     test_times = []
     test_support.use_resources = use_resources
-    save_modules = sys.modules.keys()
+    save_modules = set(sys.modules.keys())
 
     def accumulate_result(test, result):
         ok, test_time = result