IIS - how to handle file permission problem Here is a generic error message, shown several times on each page : 


  Warning: file_put_contents(temporary://fil25BC.tmp): failed to open stream: "DrupalTemporaryStreamWrapper::stream_open" call failed in > file_unmanaged_save_data() (line 1935 of C:\inetpub\www-v2.3\includes\file.inc).


What can I do ? 

EDIT
I stopped struggling with that problem by changing my temporary directory on this server
It was C:\Windows\temp (or C:\Windows\temp\drp-tmp)
It is now sites/default/files/drp-tmp
Note : on another server, the first setting is not giving warnings... Well, looks like I do not master that topic !
THANK YOU FOR your answers and attention
Seems like issue is that Drupal is trying to write a temporary file somewhere it cannot write, like in the site's docroot...

Try running below commands using drush and make sure write access is available for temp directories..

~$ drush vget file_directory_temp

~$ drush vget file_temporary_path