[Exception] Missing write permissions to the following directories: pub/static folder - MAGENTO 2

How to debug and fix:

1) setup/src/Magento/Setup/Model/FilePermissions.php

2) Goto line 143 in method checkRecursiveDirectories

3) Add the lines var_dump($subDirectory);var_dump($subDirectory->isWritable()); return false;

4) Re run bin/magento setup:upgrade

Now you'll see what is really wrong, and you can fix it. Personally i remove everything in pub/static, this will be auto generated content so you should not be worried about that.