typo fix, extra '.' on MacOS :)
diff --git a/Lib/test/test_subprocess.py b/Lib/test/test_subprocess.py
index faa153a..d747845 100644
--- a/Lib/test/test_subprocess.py
+++ b/Lib/test/test_subprocess.py
@@ -2502,7 +2502,7 @@
 
     _libc_file_extensions = {
       'Linux': 'so.6',
-      'Darwin': '.dylib',
+      'Darwin': 'dylib',
     }
     @unittest.skipIf(platform.uname()[0] not in _libc_file_extensions,
                      'Test requires a libc this code can load with ctypes.')