Drush 8 raises an error while running 'drush runserver' I just installed Drush (globally) as described here: http://docs.drush.org/en/master/install/,
on Ubuntu 14.04 (PHP 5.5.9).

Then I created a new Drupal 8 web site and database with:

$ drush dl drupal --drupal-project-rename=example
$ drush si standard \
    --db-url='mysql://[db_user]:[db_pass]@localhost/[db_name]' 
    --site-name=Example


When I run the built-in server within the project directory: 

$ drush rs 8000


And I try to access http://localhost:8000, I get this error:


  PHP Warning: Unknown: failed to open stream: phar error: invalid url or non-existent phar phar:///usr/local/bin/drush/commands/runserver/d8-rs-router.php in Unknown on line 0
  PHP Fatal error:  Unknown: Failed opening required 'phar:///usr/local/bin/drush/commands/runserver/d8-rs-router.php' (include_path='.:/usr/share/php:/usr/share/pear') in Unknown on line 0


What's wrong?
I solved installing the last version of Drush via composer:

$ # Remove previous drush installation file
$ sudo rm /usr/local/bin/drush

$ # Install drush globally via composer
$ composer global require drush/drush
$ ln -s ~/.composer/vendor/bin/drush ~/bin/drush


Now it works.