sqlalchemy: fix default integer constructor

* Addresses issue with default constructor on types that do not
  accept arguments in SQLAlchemy>=0.9. (closes #1776)

Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>
22:1: F401 'TypeDecorator' imported but unused
23:1: F401 'INTEGER' imported but unused
26:1: E302 expected 2 blank lines, found 1
36: D102 Docstring missing