Legacy algorithm warning

This merge request adds a warning when running a legacy algorithm.

They should be ported to the new API.

beat/backend/python/test/mocks.py

@@ -25,6 +25,7 @@
 #                                                                             #
 ###############################################################################
 
+import logging
 
 from collections import namedtuple
 
@@ -83,3 +84,34 @@ class MockDataSink(DataSink):
 
     def isConnected(self):
         return True
+
+# Based on https://stackoverflow.com/a/20553331/5843716
+class MockLoggingHandler(logging.Handler):
+    """Mock logging handler to check for expected logs.
+
+    Messages are available from an instance's ``messages`` dict, in order,
+    indexed by a lowercase log level string (e.g., 'debug', 'info', etc.).
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.messages = {
+            'debug': [], 'info': [],
+            'warning': [], 'error': [],
+            'critical': [], 'extra': []
+        }
+        super(MockLoggingHandler, self).__init__(*args, **kwargs)
+
+    def emit(self, record):
+        "Store a message from ``record`` in the instance's ``messages`` dict."
+        try:
+            self.messages[record.levelname.lower()].append(record.getMessage())
+        except Exception:
+            self.handleError(record)
+
+    def reset(self):
+        self.acquire()
+        try:
+            for message_list in self.messages.values():
+                message_list.clear()
+        finally:
+            self.release()