pulumi new for Python should create and activate virtual environment

[swgillespie]

Today, instantiating a Python template using pulumi new installs the Pulumi package and dependencies outside of a virtual environment, which is fraught with peril and outside of what users will expect if they intend to use virtual environments. We should consider creating a virtual environment for users when running pulumi new.

We should decide whether or not we should push pipenv on people or if we should just use virtualenv for this. Either way, we should be installing packages into a virtual environment.

[lukehoban]

I think we'll need two things here:

1. Short term - make sure that pulumi new works for Python. That may mean skipping auto-update for Python templates and printing out instructions for what to do manually.
2. Make end-to-end smooth but automatically creating virtualenv and installing dependencies so that we can go all the way to update succesfully.

[swgillespie]

Agreed. I will shoot for 1) ASAP.

[swgillespie]

The M19 component of this bug is done, moving the rest out to M20 (creating and activating a virtual environment).

[swgillespie]

Since we're not a shell, I don't believe it's particularly useful to activate a virtual environment from the CLI since a user will have to source it again anyway. If there's any demand for this feature, we can re-open this issue.