The test here always passed because SQLAlchemy has never
reflected CHECK constraints before, so the test never exercised
anything. An upcoming feature in SQLAlchemy 1.1 will allow
the Postgresql and SQLite dialects to reflect CHECK constraints,
and the existing test for the "boolean" constraint fails.
This patch repairs the test with a more generic regular expression
match and passes against all SQLAlchemy versions.
Change-Id: Idc17c39325ccfee3bbbe171ed2833a4f0991d261