Vim Can't Save File (E212)
This will ask you for the root password, then save your changes as you requested:
:w !sudo tee %
Then type (L)oad at the prompt, to re-load the file after it is saved.
Add this line to your .vimrc:
cmap w!! %!sudo tee > /dev/null
and then you can do
:w!!
when you get into this position, and it will write the file using sudo. Very handy.
You can mkdir first, then save it.