[request] Ensure base_url() always has a trailing '/' (closes #3955093)
Just as an example, cubicweb.ajax.js is clearly written under the
assumption that BASE_URL/baseuri() - which simply contains req.base_url() - has a
trailing /.
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.cu
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)