Interesting. I wasn't aware of that issue. It seems like after running activate, `pip` does point to the right location (`which pip` points to the virtualenv pip), but I'll look into it.
Unfortunately the changes you did didn't improve my problem, pip insisted again that a correct tensorflow version wasn't available. I was, however, able to download tb-nightly so I do at least have a version. Quite shocked tensorflow thrashes so intensely on installation - is that normal?
I'm glad you have found a workaround. Again, this is for an example script outside of the main narrative of the book, so the impact should be minimal.
If pip struggles to find a specific version, I'll usually remove the specific version requirement, and give whichever version pip finds a try by running `pip install tensorflow`