[source/native] fix sqlserver pattern matcher for unique constraints (closes #3227593) The matcher is used to parse the low-level error message and extract meaningful information for the end users. If broken, the users see an alarming and bewildering message. A full & definitive fix is scheduled for CubicWeb 3.18.

# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
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"""%(distname)s specific hooks and operations"""