[dbapi] move ProgrammingError into cubicweb module
A new ``repoapi`` will be introduced as a replacement for the dbapi. It will
need ProgrammingError too.
Related to #2503918
Document: cubicweb-doc
Title: CubicWeb documentation
Author: Logilab
Abstract: Some base documentation for CubicWeb users and developpers
Section: Apps/Programming
Format: HTML
Index: /usr/share/doc/cubicweb-documentation/index.html
Files: /usr/share/doc/cubicweb-documentation/*.html