Swap file "/etc/.sudoers.tmp.swp" already exists!

whilst trying to edit sudoers (sudo visudo) i get the error given below. google search provides no clear explanation or fix.

Found a swap file by the name "/etc/.sudoers.tmp.swp"
          owned by: root   dated: Mon Sep  5 22:20:21 2016
         file name: /etc/sudoers.tmp
          modified: YES
         user name: root   host name: asus
        process ID: 17293
While opening file "/etc/sudoers.tmp"
             dated: Thu Jan 19 10:51:46 2017
      NEWER than swap file!

(1) Another program may be editing the same file.  If this is the case,
    be careful not to end up with two different instances of the same
    file when making changes.  Quit, or continue with caution.
(2) An edit session for this file crashed.
    If this is the case, use ":recover" or "vim -r /etc/sudoers.tmp"
    to recover the changes (see ":help recovery").
    If you did this already, delete the swap file "/etc/.sudoers.tmp.swp"
    to avoid this message.

Swap file "/etc/.sudoers.tmp.swp" already exists!
[O]pen Read-Only, (E)dit anyway, (R)ecover, (D)elete it, (Q)uit, (A)bort: 

instead of searching google i engaged my brain, worked out it was a hanging lock file and manually deleted. Please ignore.

Yes. “vi” (or “vim”) does that. You probably aborted an earlier edit attempt.