all: update repo to use the new error handling syntax (#8950)

vlib/io/os_file_reader_test.v

@@ -3,7 +3,7 @@ import io
 
 fn read_file(file string, cap int) []string {
 	mut lines := []string{}
-	mut f := os.open(file) or { panic(err) }
+	mut f := os.open(file) or { panic(err.msg) }
 	defer {
 		f.close()
 	}

vlib/io/util/util_test.v

@@ -12,7 +12,7 @@ fn testsuite_begin() {
 	eprintln('testsuite_begin, tfolder = $tfolder')
 	os.rmdir_all(tfolder) or { }
 	assert !os.is_dir(tfolder)
-	os.mkdir_all(tfolder) or { panic(err) }
+	os.mkdir_all(tfolder) or { panic(err.msg) }
 	os.chdir(tfolder)
 	assert os.is_dir(tfolder)
 }