This plugin deletes trailing whitespaces on every write.

Using vim-plug,

Plug 'raviqqe/vim-nonblank'

A buffer ($ denotes a newline character)

foo  $
$
  $
bar baz   $
  $
$

will be normalized as below.

foo$
$
$
bar baz$

Set the enabled flag to 0.

let g:nonblank_enabled = 0

Then you can run :NonBlank command manually.

Set the blacklist flag.

let g:nonblank_blacklist = ['python']

The default value is ['diff', 'gitcommit'].

The Unlicense