patch 8.1.0247: Python: error message for failing import is incorrect

Problem:    Python: error message for failing import is incorrect.
Solution:   Adjust how modules are loaded. (Ozaki Kiichi, closes #3162)
diff --git a/src/testdir/test87.ok b/src/testdir/test87.ok
index 9ca4b62..a7d4f64 100644
--- a/src/testdir/test87.ok
+++ b/src/testdir/test87.ok
@@ -701,7 +701,7 @@
 vim.foreach_rtp(int, 2):(<class 'TypeError'>, TypeError('foreach_rtp() takes exactly one argument (2 given)',))
 > import
 import xxx_no_such_module_xxx:(<class 'ImportError'>, ImportError('No module named xxx_no_such_module_xxx',))
-import failing_import:(<class 'ImportError'>, ImportError('No module named failing_import',))
+import failing_import:(<class 'ImportError'>, ImportError())
 import failing:(<class 'NotImplementedError'>, NotImplementedError())
 > Options
 >> OptionsItem