tree_compare.py: 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/lib/qiime/bin/tree_compare.py - from package: qiime

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

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