Update error messages in sanity tests

Update error messages throughout sanity tests
to use the same (or similar) format of error message.

Change-Id: I4db0517a5b264151ddaa6ea2c2a04d37e139944e
Related-PROD: #PROD-32415
diff --git a/test_set/cvp-sanity/tests/test_nodes.py b/test_set/cvp-sanity/tests/test_nodes.py
index 6ab48df..082930e 100644
--- a/test_set/cvp-sanity/tests/test_nodes.py
+++ b/test_set/cvp-sanity/tests/test_nodes.py
@@ -16,5 +16,5 @@
         pytest.fail(
             "Could not check the result: {}\n"
             "Nodes status result: {}".format(e, result))
-    assert not statuses["down"], "Some minions are down:\n {}".format(
+    assert not statuses["down"], "Some minions are down:\n{}".format(
         statuses["down"])