Ignore VariableDoesNotExist errors in debug logging

They're so noisy as to make debug logging useless otherwise

bookwyrm/utils/log.py

@@ -0,0 +1,12 @@
+import logging
+
+
+class IgnoreVariableDoesNotExist(logging.Filter):
+    def filter(self, record):
+        if(record.exc_info):
+            (errType, errValue, _) = record.exc_info
+            while errValue:
+                if type(errValue).__name__ == 'VariableDoesNotExist':
+                    return False
+                errValue = errValue.__context__
+            return True