deploy.py should prepend to PYTHONPATH or we get confusing errors

$ time ./juju-deployer/deploy.py
Checking juju status
Uploading local branch to swift ...
No handlers could be found for logger "keystoneclient.httpclient"
Building charm: rabbitmq-worker
rm -fr hooks/charmhelpers build/charm-helpers ../.sourcecode
Updating source dependencies...
           build/charm-helpers: checked out r99 of lp:~charm-helpers/charm-helpers/devel
INFO:root:Loading charm helper config from charm-helpers.yaml.
INFO:root:Checking out build/charm-helpers to /tmp/tmpL0iTvC/charm-helpers.
Branched 99 revisions.
INFO:root:Syncing directory: /tmp/tmpL0iTvC/charm-helpers/charmhelpers/core -> hooks/charmhelpers/core.
INFO:root:Adding missing __init__.py: hooks/charmhelpers/__init__.py
INFO:root:Syncing directory: /tmp/tmpL0iTvC/charm-helpers/charmhelpers/fetch -> hooks/charmhelpers/fetch.
INFO:root:Syncing directory: /tmp/tmpL0iTvC/charm-helpers/charmhelpers/contrib/charmsupport -> hooks/charmhelpers/contrib/charmsupport.
INFO:root:Adding missing __init__.py: hooks/charmhelpers/contrib/__init__.py
Do not forget to commit the updated files if any.
#@cd /home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/rabbitmq-worker/build/charm-helpers; \
  #@/usr/bin/env python setup.py install --install-purelib=/home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/rabbitmq-worker/lib \
   #--install-scripts=/home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/rabbitmq-worker/lib/bin
Building charm: webui
rm -fr hooks/charmhelpers build/charm-helpers files/webroot revision ../.sourcecode
Updating source dependencies...
           build/charm-helpers: checked out r99 of lp:~charm-helpers/charm-helpers/devel
INFO:root:Loading charm helper config from charm-helpers.yaml.
INFO:root:Checking out build/charm-helpers to /tmp/tmpjQ7XSZ/charm-helpers.
Branched 99 revisions.
INFO:root:Syncing directory: /tmp/tmpjQ7XSZ/charm-helpers/charmhelpers/core -> hooks/charmhelpers/core.
INFO:root:Adding missing __init__.py: hooks/charmhelpers/__init__.py
INFO:root:Syncing directory: /tmp/tmpjQ7XSZ/charm-helpers/charmhelpers/fetch -> hooks/charmhelpers/fetch.
INFO:root:Syncing directory: /tmp/tmpjQ7XSZ/charm-helpers/charmhelpers/contrib/charmsupport -> hooks/charmhelpers/contrib/charmsupport.
INFO:root:Adding missing __init__.py: hooks/charmhelpers/contrib/__init__.py
Do not forget to commit the updated files if any.
#@cd /home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/webui/build/charm-helpers; \
  #@/usr/bin/env python setup.py install --install-purelib=/home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/webui/lib \
   #--install-scripts=/home/vila/ci/ubuntu-ci-services-itself/trunk/charms/precise/webui/lib/bin
Running juju-deployer -v -c /tmp/tmpQAWMDF/deployer/ticket-system.yaml -c /tmp/tmpQAWMDF/deployer/ppa-assigner.yaml -c /tmp/tmpQAWMDF/deployer/test-runner.yaml -c /tmp/tmpQAWMDF/deployer/image-builder.yaml -c /tmp/tmpQAWMDF/deployer/branch-source-builder.yaml -c /tmp/tmpQAWMDF/deployer/lander.yaml -c /tmp/tmpQAWMDF/deployer/relations.yaml -c /tmp/tmpQAWMDF/deployer/juju-gui.yaml -c /tmp/tmpQAWMDF/deployer/production-only.yaml ci-airline-staging
Traceback (most recent call last):
  File "/tmp/tmpbBopcg/deployer/cli.py", line 20, in <module>
    from deployer.utils import ErrorExit, setup_logging, get_env_name
ImportError: cannot import name get_env_name
Problem deploying "ci-airline-staging": Command '['juju-deployer', '-v', '-c', '/tmp/tmpQAWMDF/deployer/ticket-system.yaml', '-c', '/tmp/tmpQAWMDF/deployer/ppa-assigner.yaml', '-c', '/tmp/tmpQAWMDF/deployer/test-runner.yaml', '-c', '/tmp/tmpQAWMDF/deployer/image-builder.yaml', '-c', '/tmp/tmpQAWMDF/deployer/branch-source-builder.yaml', '-c', '/tmp/tmpQAWMDF/deployer/lander.yaml', '-c', '/tmp/tmpQAWMDF/deployer/relations.yaml', '-c', '/tmp/tmpQAWMDF/deployer/juju-gui.yaml', '-c', '/tmp/tmpQAWMDF/deployer/production-only.yaml', 'ci-airline-staging']' returned non-zero exit status 1

real 52m23.976s
user 0m45.369s
sys 0m5.246s

The root cause is that I had a different version of juju-deployer locally installed and importable from PYTHONPATH.

"/tmp/tmpbBopcg/deployer/cli.py" was used because it's the script entry point but then the modules were imported from the wrong version.