tests: Enable SAWarning warnings

We shouldn't be raising warnings from SQLAlchemy. Where we are
intentionally doing so, we should capture these warnings at the test
level. This requires some minor fixes.

Change-Id: I9d4512dc337153edc48a2cc3bf95ab2b31c39ccf
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

oslo_db/sqlalchemy/utils.py

@@ -39,6 +39,7 @@ from sqlalchemy import Index
 from sqlalchemy import inspect
 from sqlalchemy import Integer
 from sqlalchemy import MetaData
+from sqlalchemy import PrimaryKeyConstraint
 from sqlalchemy.sql.expression import cast
 from sqlalchemy.sql.expression import literal_column
 from sqlalchemy.sql import text
@@ -608,7 +609,14 @@ def _change_deleted_column_type_to_boolean_sqlite(engine, table_name,
 
     # FIXME(stephenfin): We shouldn't be using this private API;
     # figure out how else to copy an arbitrary column schema
-    constraints = [constraint._copy() for constraint in table.constraints]
+    # NOTE(stephenfin): We drop PrimaryKeyConstraint-type constraints since
+    # these duplicate the 'primary_key=True' attribute on the speicified
+    # column(s). This technically breaks things when the primary key covers
+    # multiple columns but that's okay: these are deprecated APIs
+    constraints = [
+        constraint._copy() for constraint in table.constraints
+        if not isinstance(constraint, PrimaryKeyConstraint)
+    ]
 
     with engine.connect() as conn:
         meta = table.metadata
@@ -738,7 +746,10 @@ def _change_deleted_column_type_to_id_type_sqlite(engine, table_name,
 
     constraints = []
     for constraint in table.constraints:
-        if not _is_deleted_column_constraint(constraint):
+        if not (
+            _is_deleted_column_constraint(constraint) or
+            isinstance(constraint, PrimaryKeyConstraint)
+        ):
             # FIXME(stephenfin): We shouldn't be using this private API;
             # figure out how else to copy an arbitrary constraint schema
             constraints.append(constraint._copy())
@@ -749,7 +760,8 @@ def _change_deleted_column_type_to_id_type_sqlite(engine, table_name,
         with conn.begin():
             new_table = Table(
                 table_name + "__tmp__", meta,
-                *(columns + constraints))
+                *(columns + constraints),
+            )
             new_table.create(conn)
 
         indexes = []

oslo_db/tests/fixtures.py

@@ -24,11 +24,12 @@ class WarningsFixture(fixtures.Fixture):
 
         self._original_warning_filters = warnings.filters[:]
 
-        # Make deprecation warnings only happen once to avoid spamming
         warnings.simplefilter('once', DeprecationWarning)
 
+        # Enable generic warnings to ensure we're not doing anything odd
+
         warnings.filterwarnings(
-            'error', message='Evaluating non-mapped column expression',
+            'error',
             category=sqla_exc.SAWarning)
 
         # Enable deprecation warnings to capture upcoming SQLAlchemy changes