fix unit test case

Author: TejasMorbagal

test/test_store.py

@@ -194,11 +194,11 @@ def test_store_for_cmems_credentials(self):
         with self.assertRaises(Exception) as e:
             CmemsDataStore(**params)
         self.assertEqual(
-            "CmemsDataStore needs cmems credentials to "
-            "be provided either as "
-            "environment variables CMEMS_USERNAME and "
-            "CMEMS_PASSWORD, or to be "
-            "provided as store params cmems_username and "
-            "cmems_password",
+             "CmemsDataStore needs cmems credentials to "
+                "be provided either as "
+                "environment variables COPERNICUSMARINE_SERVICE_USERNAME and "
+                "COPERNICUSMARINE_SERVICE_PASSWORD, or to be "
+                "provided as store params cmems_username and "
+                "cmems_password",
             f"{e.exception}",
         )