filter expert: add debugging output for comparisons

if users or devs run the bot in DEBUG log level, there was no useful
output yet.
This change adds two log statements, showing which comparision was made

intelmq/bots/experts/filter/expert.py

@@ -148,10 +148,12 @@ def doFilter(self, event, key, condition):
             return self.equalsFilter(event, key, condition)
 
     def equalsFilter(self, event, key, value):
+        self.logger.debug('Equality check: %r (event value) == %r (filter value).', event.get(key), value)
         return (key in event and
                 event.get(key) == value)
 
     def regexSearchFilter(self, event, key):
+        self.logger.debug('Regex filter: Matching %r against %r.', str(event.get(key)), self.filter_value)
         if key in event:
             return self.regex.search(str(event.get(key)))
         else: