Message 281500 - Python tracker (original) (raw)
I disagree that the documentation is at fault. This is known to break existing code, e.g. http://bugs.python.org/msg281496
I think it's not correct to change the documentation but leave the error-raising behavior for 3.6 because the deprecation was never documented in 3.5 so this will look like a gratuitous regression. for reference.
I also question whether it makes sense for such escapes to be illegal in the repl argument of re.sub(). I could understand for this limitation in the pattern argument, but that's not what's causing the error.