Enable debug mode in tests.

Debug mode allows route integration tests to raise explicit exceptions on
errors, instead of returning error pages. Some portions of the test
suite need to be able to ignore exceptions (the response is not under
test) so they use a separate pytest fixture version of the app and
client that are configured with debug disabled, as it would be in
production.

tests/routes/portfolios/test_admin.py

@@ -1,5 +1,5 @@
 from flask import url_for
-from unittest.mock import Mock
+from unittest.mock import MagicMock
 
 from atst.domain.permission_sets import PermissionSets
 from atst.domain.portfolio_roles import PortfolioRoles
@@ -129,7 +129,7 @@ def test_rerender_admin_page_if_member_perms_form_does_not_validate(
         "members_permissions-0-perms_portfolio_mgmt": "view_portfolio_admin",
     }
 
-    mock_route = Mock()
+    mock_route = MagicMock(return_value=("", 200, {}))
     monkeypatch.setattr("atst.routes.portfolios.admin.render_admin_page", mock_route)
     client.post(
         url_for("portfolios.edit_members", portfolio_id=portfolio.id), data=form_data