Allow test_pathlib to pass on systems where fakeuser exists. (GH-30244)

(cherry picked from commit d8880677a79ba4e70bbe7583eecf573bfceb7e98)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
diff --git a/Lib/test/test_pathlib.py b/Lib/test/test_pathlib.py
index 5f6d9f4..2268d36 100644
--- a/Lib/test/test_pathlib.py
+++ b/Lib/test/test_pathlib.py
@@ -2564,7 +2564,7 @@ def test_expanduser(self):
         p4 = P('../~' + username + '/Documents')
         p5 = P('/~' + username + '/Documents')
         p6 = P('')
-        p7 = P('~fakeuser/Documents')
+        p7 = P('~fake800813user/Documents')
 
         with os_helper.EnvironmentVarGuard() as env:
             env.pop('HOME', None)