patch 8.1.1346: error for Python exception does not show useful info

Problem:    Error for Python exception does not show useful info.
Solution:   Show the last line instead of the first one. (Ben Jackson,
            closes #4381)

src/testdir/test_python2.vim

@@ -160,3 +160,11 @@ func Test_Write_To_Current_Buffer_Fixes_Cursor_Str()
 
   bwipe!
 endfunction
+
+func Test_Catch_Exception_Message()
+  try
+    py raise RuntimeError( 'TEST' )
+  catch /.*/
+    call assert_match( '^Vim(.*):RuntimeError: TEST$', v:exception )
+  endtry
+endfunc