Restore write permission on sites/default and settings.php

When Drupal is build for the second (third, etc.) time, it is necessary to restore write permission on site settings.php file, because it is removed by Drupal by default.

Otherwise Drush make command will fail to copy all files to the src/drupal/.

drush.py

@@ -19,6 +19,8 @@
 from __future__ import unicode_literals
 from datetime import datetime
 
+import os
+
 from fabric.api import task, roles, env, local
 from fabric.colors import red, green
 from fabric.contrib.console import confirm
@@ -63,6 +65,12 @@ def make(action='install'):
         local('mkdir {}'.format(env.site_root))
 
     with h.fab_cd('local', env.site_root):
+        if os.path.isdir('{}/sites/default/'.format(env.site_root)):
+            local('chmod u+w sites/default')
+
+        if os.path.isfile('{}/sites/default/settings.php'.format(env.site_root)):
+            local('chmod u+w sites/default/settings.php')
+
         local('drush make {} {} -y'.format(drush_opts, env.makefile))