[predicates] keep making `yes` predicate importable from cubicweb (closes #2790319)
The `yes` predicate was moved out in CubicWeb 3.15 but it should have
remained importable from the cubicweb.predicates module, for bw compat
reasons and also because logilab.common.registry is an implementation
detail.
from yams import schema2sql as y2sql
dbhelper = repo.system_source.dbhelper
rdefdef = schema['CWSource'].rdef('name')
attrtype = y2sql.type_from_constraints(dbhelper, rdefdef.object, rdefdef.constraints).split()[0]
cursor = session.cnxset['system']
sql('UPDATE entities SET asource = source WHERE asource is NULL')
dbhelper.change_col_type(cursor, 'entities', 'asource', attrtype, False)
dbhelper.change_col_type(cursor, 'entities', 'source', attrtype, False)
dbhelper.change_col_type(cursor, 'deleted_entities', 'source', attrtype, False)