Issuing the command
drush vset maintenance_mode 1
gives me an error:
Deprecated function: Array and string offset access syntax with curly[error] braces is deprecated in include_once() (line 20 of /usr/share/drupal/includes/file.phar.inc).
I am wondering if I have to upgrade drush for getting rid of that error. I tried anyway to issue:
drush dl drush
At the prompt, I gave 1 as answer. I got next output. Again errors, even if it outputs
[success] at the end.
There are no stable releases for project drush. [warning] Choose one of the available releases for drush: count(): Parameter must be an array or an object that implements [warning] Countable Table.php:789 count(): Parameter must be an array or an object that implements [warning] Countable Table.php:789  : Cancel  : 8.x-6.x-dev - 2013-Sep-30 - Development 1 Unable to extract [error] /tmp/drush_tmp_1603203813_5f8ef2e5117e3/drush-8.x-6.x-dev.tar.gz_date=1380571116. Unknown archive format. Project drush (8.x-6.x-dev) downloaded to /home/pf/drush. [success] Project drush contains 0 modules: .
I am a little bit stuck since everything I try is going wrong. A little help would be highly appreciated.