Fix `no such file or directory` error on wercker-labs/docker box
Fix `no such file or directory` error on wercker-labs/docker box

dlanileonardo/step-pretty-slack-notify,wantedly/step-pretty-slack-notify,wantedly/step-pretty-slack-notify,wantedly/step-pretty-slack-notify,dlanileonardo/step-pretty-slack-notify,dlanileonardo/step-pretty-slack-notify