your devtools package is a version below 1.4, and it should work if updated (admittedly, that is quite the apologetic standard answer, but probably worth checking).
alternatively, try the format install_github("MonoPhy", username="oschwery")to force the right username on it.
Installing dev version using 'install_github' fails because username in path is not recognized and 'hadley' is used before 'oschwery'.