pip should return non-zero exit status on error "can't proceed... due to a pre-existing build directory"

[cypreess]

pip should return non-zero exit status after erroring on "can't proceed... due to a pre-existing build directory"

Returning ZERO exit status give false positive behaviour in automation scripting (e.g. ansible provisioning)

Downloading/unpacking Django==1.4.8 (from -r /vagrant/project/requirements.pip (line 1))

pip can't proceed with requirement 'Django==1.4.8 (from -r /vagrant/project/requirements.pip (line 1))' due to a pre-existing build directory.
 location: /home/vagrant/venv/build/Django
This is likely due to a previous installation that failed.
pip is being responsible and not assuming it can delete this.
Please delete it and try again.

Cleaning up...
vagrant@precise64:~$ echo $?
0

[cypreess]

Sorry, this issue is duplicate of already solved issue: #1208 in dev branch