PY_VER is already calculated in this fashion above on line 28 (https://github.com/iandanforth/nupic/blob/735e05a76beebd4f29aa145dd1be28735cfa6b2e/env.sh#L28).  I would recommend revising that line to specify PY_VERSION, export it, and update the reference on line 39 (https://github.com/iandanforth/nupic/blob/735e05a76beebd4f29aa145dd1be28735cfa6b2e/env.sh#L39) instead of having both PY_VER and PY_VERSION.

Otherwise, looks good to me.