bpo-37834: Fix test on Windows 7 (GH-15377)

diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index ba9f5c3..4285931 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -2466,6 +2466,9 @@
 
     def test_appexeclink(self):
         root = os.path.expandvars(r'%LOCALAPPDATA%\Microsoft\WindowsApps')
+        if not os.path.isdir(root):
+            self.skipTest("test requires a WindowsApps directory")
+
         aliases = [os.path.join(root, a)
                    for a in fnmatch.filter(os.listdir(root), '*.exe')]