'Drop a foreign key constraint'

@invalidate_table_constraints
def delete_foreign_key(self, table_name, column):

    if self.dry_run:
        if self.debug:
            print('            -    no    dry    run    output    for    delete_foreign_key()    due    to    dynamic    DDL,    sorry')
        return
    constraints = self._find_foreign_constraints(table_name, column)
    if (not constraints):
        raise ValueError(('Cannot    find    a    FOREIGN    KEY    constraint    on    table    %s,    column    %s' % (table_name, column)))
    for constraint_name in constraints:
        self.execute((self.delete_foreign_key_sql % {'table': self.quote_name(table_name), 'constraint': self.quote_name(constraint_name)}))
