BF: test_scripts -- provide PYTHONPATH to use current nibabel.  Closes #200

to avoid testing scripts against installed version of nibabel
RF: set PYTHONPATH only for local script testing

We only want to promote the local nibabel installation if we're testing
local scripts.
Merge branch 'ymaster' into main-master

* ymaster:
  RF: set PYTHONPATH only for local script testing
  BF: test_scripts -- provide PYTHONPATH to use current nibabel.  Closes #200