use abstract base class

src/sources.py

@@ -1,13 +1,16 @@
 import datetime
+from abc import ABCMeta, abstractmethod
+from collections import namedtuple
+
 import requests
 
-from collections import namedtuple
 
 Status = namedtuple("Status", ['doorstate', 'timestamp', 'text'])
 
-class Source:
+class Source(metaclass=ABCMeta):
+	@abstractmethod
 	def get_status(self):
-		raise NotImplementedError()
+		pass
 	
 	def is_recent(self, status, **kwargs):
 		return status.timestamp + datetime.timedelta(days=1) < datetime.datetime.today()

src/targets.py

@@ -1,4 +1,5 @@
 import logging
+from abc import ABCMeta, abstractmethod
 
 import requests
 
@@ -6,9 +7,10 @@ from matrix_client.client import MatrixClient as MatrixApiClient
 from matrix_client.errors import MatrixError
 
 
-class Client:
+class Client(metaclass=ABCMeta):
+	@abstractmethod
 	def __init__(self):
-		raise NotImplementedError()
+		pass
 	
 	def post_image(self, file, name, content_type="image/png", targets=None):
 		"""Push to all targets"""