* fix argv0 reference counter if PyList_SetItem() fails
 * don't use complex if conditions, but a simple indentation and "goto error"
 * simplify error handling (remove Py_XDECREF(importer) from the error label)
 * don't set sys_path to NULL (it's useless, sys_path is a borrowed reference
   and sys_path is not a static variable)
 * try to write only one instruction per line for better readability