Activate virtualenv in Makefile

Question

Here’s how to do it:

You can execute a shell command in a Makefile using ();

E.g.

echoTarget: 
    (echo "I'm an echo")

Just be sure to put a tab character before each line in the shell command.
i.e. you will need a tab before (echo “I’m an echo”)

Here’s what will work for activating virtualenv:

activate:
    ( \
       source path/to/virtualenv/activate; \
       pip install -r requirements.txt; \
    )