How do I update a virtualenv?

[Skip Montanaro]

>> I have a virtualenv I'm using for some Django development.  Today I
>> switched from MacPorts to HomeBrew on my Mac.
>
> Any particular reason for doing that?  That seems like a step backwards,
> especially for Python-related work.

The guy who sits next to me at work recommended HomeBrew. (Someone to
ask for help. :-) I didn't have all that much stuff installed via
MacPorts, buncha libraries mostly, so it didn't seem like a huge
sacrifice. Also, when I'd tried installing gcc 4.8 a few weeks ago
things didn't go so well, so I figured I'd try HomeBrew.

Skip