Control File: invalid package urgency
When you create a control file for a package, you are expected to define the Urgency field. If you are writing a changelog file, then the urgency is the same as what you define in your changelog.
The urgency is used to define how important it is to install a new version of a package. "critical" and "emergency" should really only be used for things such as security updates. Other priorities will depend on your need.
Only the defined set of urgencies are valid. All other words are considered invalid and generate an error.
VALIDUrgency: critical
Urgency: medium
INVALIDUrgency: important
Urgency: immediate
Urgency: 911