gdk_pixbuf_mlsource: 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 CentOS possible default full paths are:

/usr/bin/gdk_pixbuf_mlsource - from package: ocaml-lablgtk

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/gdk_pixbuf_mlsource - from package: liblablgtk2-ocaml-dev

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

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