VI – How to Edit Default vimrc File (Read-Only, Operation Not Permitted)

How can I edit the default vimrc file on osx? (sudo chown … gives Operation not permitted )

In osx vim /usr/share/vim/vimrc is the default vimrc file

My username is 'apple'

If I try to do vim /usr/share/vim/vimrc then it says 'read only'

~/.vim$ ls -l /usr/share/vim/vimrc
-rw-r–r– 1 root wheel 532 5 Apr 2017 /usr/share/vim/vimrc
~/.vim$

If I try to change ownership of the file

~/.vim$ sudo chown apple /usr/share/vim/vimrc 
chown: /usr/share/vim/vimrc: Operation not permitted
~/.vim$ 

similarly with permissions (giving write access to non-root users temporarily for the purposes of me editing the file)

~/.vim$ sudo chmod 666 /usr/share/vim/vimrc
chmod: Unable to change file mode on /usr/share/vim/vimrc: Operation not permitted
~/.vim$ 

sudo chown does work on another file though, so it's not a password issue.

~/.vim$ cp /usr/share/vim/vimrc zzz
~/.vim$ ls -l zzz
-rw-r--r--  1 apple  staff  532  3 May 23:10 zzz
~/.vim$ sudo chown root zzz
~/.vim$ sudo chown apple zzz
~/.vim$