Setting up a transparent proxy on OSX El Capitan

Hi guys. I’m new to working with mitmproxy and relatively new to UNIX-stuff too so apologies if this seems stupid.

I’m trying to use mitmproxy to debug an app of mine, but am running into trouble when setting up transparent mode on my Mac (OSX El Capitan 10.11.6). I’ve created a .conf file with the relevant redirection rules for pf in the /etc/ directory, but when attempting to configure them in terminal, I get the following.

pfctl: Use of -f option, could result in flushing of rules
present in the main ruleset added by the system at startup.
See /etc/pf.conf for further details.

No ALTQ support in kernel
ALTQ related functions disabled
pfctl: /etc/ No such file or directory
pfctl: cannot open the main config file!: No such file or directory
pfctl: Syntax error in config file: pf rules not loaded

The contents of the config file are identical to the tutorial. I think the error may be related to the System Integrity Protection added to the latest OS update, but I’m unsure of how to get around these.