cabal-rpm-diff: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/cabal-rpm-diff - from package: cabal-rpm

You may install the required package with command yum install {package}
Error in other languages:
cabal-rpm-diff: bevel nie gevind nie
cabal-rpm-diff: comandă negăsită
cabal-rpm-diff: comando não encontrado
cabal-rpm-diff: commande introuvable
cabal-rpm-diff: command not found
cabal-rpm-diff: käsku ei ole
cabal-rpm-diff: không tìm thấy lệnh
cabal-rpm-diff: komanda nerasta
cabal-rpm-diff: Kommando nicht gefunden.
cabal-rpm-diff: kommandot finns inte
cabal-rpm-diff: komut yok
cabal-rpm-diff: nie znaleziono polecenia
cabal-rpm-diff: níor aimsíodh an t-ordú
cabal-rpm-diff: no se encontró la orden
cabal-rpm-diff: no s'ha trobat l'ordre
cabal-rpm-diff: opdracht niet gevonden
cabal-rpm-diff: parancs nem található
cabal-rpm-diff: perintah tidak ditemukan
cabal-rpm-diff: príkaz nenájdený
cabal-rpm-diff: příkaz nenalezen
cabal-rpm-diff: команда не найдена
cabal-rpm-diff: командата не е открита
cabal-rpm-diff: 命令找不到
cabal-rpm-diff: コマンドが見つかりません