dscl appending a UniqueID to a user failing in 10.15

Commands that worked in 10.14

dscl . -create /Users/$user_name

dscl . -append /Users/$user_name UserShell /usr/bin/false

dscl . -append /Users/$user_name UniqueID $new_uid

dscl . -append /Users/$user_name PrimaryGroupID 80

dscl . -append /Users/$user_name Password \*

dscl . -append /Users/$user_name NFSHomeDirectory /var/empty

dscl . -append /Users/$user_name RealName ‘DevelopmentServer'

Now

dscl . -append /Users/$user_name UniqueID $new_uid

throws the error

<main> attribute status: eDSPermissionError

<dscl_cmd> DS Error: -14120 (eDSPermissionError)

Is there something I need to change to be able to create the user?