fix_include: command not found

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 Debian possible default full paths are:

/usr/bin/fix_include - from package: iwyu

You may install the required package with command apt-get install {package}

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