Upgrading brew in El Capitan I just upgraded to El Capitan, and when I tried updating brew I got the following error:

$ brew update
Error: The /usr/local directory is not writable.
Even if this directory was writable when you installed Homebrew, other
software may change permissions on this directory. Some versions of the
"InstantOn" component of Airfoil are known to do this.

You should probably change the ownership and permissions of /usr/local
back to your user account.
  sudo chown -R $(whoami):admin /usr/local


Before I proceed with the chown recommendation, given that El Capitan just came out, is that the right way to proceed here? Why is this step necessary, and what are any potential undesirable consequences of running this command?

In case it helps, I found two issues about El Capitan in brew: 40837 and 41665 but a solution to this problem wasn't immediately clear. What can I do to continue to use brew in El Capitan reliably?
I mean they give you the solution right there. I had the same problem and I just ran:

  sudo chown -R $(whoami):admin /usr/local


and it worked.