alphagov/backdrop — pull request #189 by paulfurley (2013-12-10 14:56:21+00:00)
Title: Don't overwrite the virtualenv if exists

If you run ``bowl backdrop_read`` and ``bowl backdrop_write``
simultaneously both processes were trying to create the virtualenv. This
caused file locking errors on the Python executable.

(This also fixes the ``bowl backdrop`` which was failing)