.pylintrc: Silence some pylint warnings.

This codebase must remain py2 compatible for some more, so do not complain
about backward-compatible code.

.pylintrc

@@ -13,6 +13,7 @@ disable=
   invalid-name,
   bad-continuation,
   bad-whitespace,
+  consider-using-f-string,
   too-few-public-methods,
   too-many-locals,
   too-many-branches,
@@ -21,6 +22,7 @@ disable=
   useless-object-inheritance,
   unnecessary-pass,
   raise-missing-from,
+  redundant-u-string-prefix,
   super-with-arguments
 
 [FORMAT]