frontend: print an error message when the specified script file cannot be opened

bshell/main.c

@@ -77,6 +77,15 @@ int main(int argc, const char **argv)
 		status = bshell_file_open(argv[1], &file);
 		linesrc = &file->f_base;
 		interactive = false;
+
+		if (!FX_OK(status)) {
+			fprintf(stderr,
+			        "%s: cannot open '%s': %s\n",
+			        argv[0],
+			        argv[1],
+			        bshell_status_get_description(status));
+			return -1;
+		}
 	} else {
 #if BSHELL_INTERACTIVE == 1
 		ed = line_ed_create();