test: add 'nodb' test runner

ensure things work as expected if sqlalchemy is not installed

tests/test_app.py

@@ -7,10 +7,9 @@ import warnings
 from unittest import TestCase
 from unittest.mock import patch, MagicMock
 
-import sqlalchemy as sa
-from sqlalchemy import orm
+import pytest
 
-from wuttjamaican import app, db
+from wuttjamaican import app
 from wuttjamaican.conf import WuttaConfig
 
 
@@ -46,6 +45,11 @@ class TestAppHandler(TestCase):
         shutil.rmtree(tempdir)
 
     def test_make_session(self):
+        try:
+            from wuttjamaican import db
+        except ImportError:
+            pytest.skip("test is not relevant without sqlalchemy")
+
         session = self.app.make_session()
         self.assertIsInstance(session, db.Session.class_)
 
@@ -60,6 +64,12 @@ class TestAppHandler(TestCase):
                     foo='bar', factory=self.app.make_session)
 
     def test_get_setting(self):
+        try:
+            import sqlalchemy as sa
+            from sqlalchemy import orm
+        except ImportError:
+            pytest.skip("test is not relevant without sqlalchemy")
+
         Session = orm.sessionmaker()
         engine = sa.create_engine('sqlite://')
         session = Session(bind=engine)