cubicweb #2015073 migration to 3.13.8 crashes with sqlserver backend [resolved]

Root cause: cmd_change_attribute_type does its own SQL cooking instead of using dbhelper

priorityimportant
typebug
done in3.13.9
load left0.000
closed by#deb596dc343a [migraction] fix cmd_change_attribute_type command (closes #2015073)