Remove pragma no cover from code

Add exclude_lines in the report section of .coveragerc to ignore
abstract in test coverage

Change-Id: I7863a8ba7e20358fb7cdf3cc7e4d83871a5104ef

watcher/decision_engine/planner/base.py

@@ -33,5 +33,4 @@ class BasePlanner(object):
         and performance requirements are met.
         """
         # example: directed acyclic graph
-        raise NotImplementedError(
-            "Should have implemented this")  # pragma:no cover
+        raise NotImplementedError()