Heapy can't work before Ruby 2.3
Heapy can't work before Ruby 2.3

Since it uses the safe navigation operator that was introduced in that version: 
https://github.com/schneems/heapy/blob/e21be68fa11421afd78f3a4b61bdc2fbe79ab00e/lib/heapy/alive.rb#L133
schneems/heapy