tests: check env vars are present before starting tests

Previously it would just get None values and try to connect using those.

This can be avoided by checking the env vars are present earlier and not starting.

Closes #60

tests/conftest.py

@@ -10,12 +10,19 @@
 @pytest.fixture(scope="session")
 def settings():
     """Fixture that returns the Pyramid settings dict."""
+    # Take a copy before adding keys.
     test_settings = dict(sambal.SETTINGS)
     test_settings["samba.host"] = os.getenv("SAMBAL_TEST_HOST")
     test_settings["samba.username"] = os.getenv("SAMBAL_TEST_USERNAME")
     test_settings["samba.password"] = os.getenv("SAMBAL_TEST_PASSWORD")
     test_settings["samba.realm"] = os.getenv("SAMBAL_TEST_REALM")
     test_settings["http_host"] = "example.com"
+
+    # Verify that all env vars are present before starting.
+    assert test_settings["samba.host"] is not None
+    assert test_settings["samba.username"] is not None
+    assert test_settings["samba.password"] is not None
+    assert test_settings["samba.realm"] is not None
     return test_settings