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/strategy/context/base.py

@@ -24,5 +24,4 @@ import six
 class BaseStrategyContext(object):
     @abc.abstractmethod
     def execute_strategy(self, model):
-        raise NotImplementedError(
-            "Should have implemented this")  # pragma:no cover
+        raise NotImplementedError()

watcher/decision_engine/strategy/selection/base.py

@@ -24,5 +24,4 @@ import six
 class BaseSelector(object):
     @abc.abstractmethod
     def define_from_goal(self, goal_name):
-        raise NotImplementedError(
-            "Should have implemented this")  # pragma:no cover
+        raise NotImplementedError()