new = models.ForeignKey('news.New')
(.virtualenv) $ cat requirements.txt
Django==1.9
dj-database-url==0.3.0
psycopg2==2.6.1
wheel==0.2.6
Стало:(.virtualenv) $ cat requirements.txt
Django
dj-database-url
psycopg2
wheel
Проверяем: (.virtualenv) $ pip install -r requirements.txt
Requirement already satisfied (use --upgrade to upgrade): Django in ./.virtualenv/lib/python3.4/site-packages (from -r requirements.txt (line 1))
Requirement already satisfied (use --upgrade to upgrade): dj-database-url in ./.virtualenv/lib/python3.4/site-packages (from -r requirements.txt (line 2))
Requirement already satisfied (use --upgrade to upgrade): psycopg2 in ./.virtualenv/lib/python3.4/site-packages (from -r requirements.txt (line 3))
Requirement already satisfied (use --upgrade to upgrade): wheel in ./.virtualenv/lib/python3.4/site-packages (from -r requirements.txt (line 4))
Cleaning up...
Как видим, pip ожидаемо не стал качать ничего, что не противоречит требованиям.