Incorrect check for dependencies in python/django assistant

[xsuchy]

Reproducer:

1. Make sure python-django14 is installed and python-django is not installed.
2. run python/django assitent

It fails with:

/bin/sh: django-admin: command not found

That is because python-django14 provides python-django, but does not provide /usr/bin/django-admin and instead provides /usr/bin/django14-admin