How to install provided packages ?

I am trying to install/ use mosquitto 1.6.3



I get message "<span style="background-color: #222222; color: #f1f1f1; font-family: Monaco, monospace; font-size: 12px; white-space: pre-wrap;">Provision started</span>

<br style="box-sizing: border-box; color: #f1f1f1; font-family: Monaco, monospace; font-size: 12px; white-space: pre-wrap;" />Running provision for package mosquitto1.6.4 version: 1.6.4 by ahmedn <br style="box-sizing: border-box; color: #f1f1f1; font-family: Monaco, monospace; font-size: 12px; white-space: pre-wrap;" />./xshellz_provision1597516466: line 14: username: unbound variable

<span style="background-color: #222222; color: #f1f1f1; font-family: Monaco, monospace; font-size: 12px; white-space: pre-wrap;">Provision finished</span>

"



COuld not get what it means.



Thanks