Correct (partially) change 8736714 so the ALTER SEQUENCE  OWNED BY statement will be generated only if the sequence doesn't already have an owner_table/ owner_column (see issue #157).
Correct (partially) change 8736714 so the ALTER SEQUENCE  OWNED BY statement
will be generated only if the sequence doesn't already have an owner_table/
owner_column (see issue #157).

  TODO: Change Sequence constructor so that owner_table/owner_column (and
  other attributes) are always present in a Sequence instance, so that
  hasattr logic can be eliminated and we can also implement potential
  changes in OWNED BY.

perseas/Pyrseas,dvarrazzo/Pyrseas