Error: The following directories are not writable by your user:
You should change the ownership of these directories to your user.
sudo chown -R $(whoami) /usr/local/share/man/man8
And make sure that your user has write permission.
chmod u+w /usr/local/share/man/man8
sudo chown -R `whoami`:admin /usr/local/bin sudo chown -R `whoami`:admin /usr/local/share