test: fix match when 3.15 produces better diagnostic. (second case)

Author: rouilj

test/test_cgi.py

@@ -3791,10 +3791,7 @@ def testExpandfile(self):
             r"^Found an incorrect token when expandfile applied "
             r"string subsitution on "
             r"'[^']*[\\/]_test_template[\\/]html[\\/]file_with_bare_%.js'. "
-            r"ValueError\("
-            r"'unsupported format character ' ' \(0x20\) at index 12'\) was "
-            r"raised. Check the format "
-            r"of your named conversion specifiers."))
+            r"ValueError\("))
         self._caplog.clear()
         r = None