change abc to raise NotImplementedError for tests

.coveragerc

@@ -0,0 +1,7 @@
+[report]
+exclude_lines =
+    # Have to re-enable the standard pragma
+    pragma: no cover
+
+    # Don't complain if tests don't hit defensive assertion code:
+    raise NotImplementedError

panaetius/logging.py

@@ -98,11 +98,11 @@ class LoggingData(metaclass=ABCMeta):
     @property
     @abstractmethod
     def format(self) -> str:
-        pass
+        raise NotImplementedError
 
     @abstractmethod
     def __init__(self, logging_level: str):
-        self.logging_level = logging_level
+        raise NotImplementedError
 
 
 class SimpleLogger(LoggingData):