I have a Vagrant running Linux and I\'m trying to install Symfony.
After the command composer create-project symfony/framework-standard-edition ./ \"2.5.*\"
Wow, I can't believe how long it took me to realize this, and sadly it has happened multiple times, and I'm finally writing this note so that I and others can quickly recover next time.
Just use Windows Explorer to go delete the /vendor/whatever_project_name folder instead of trying to delete it from the Vagrant command line.
Then run composer update to reinstall the dependencies.