New issue 1287: New camera position cannot be aligned with north_vector that was used in
previous invocation of set_position
Load any data set. The following script will produce an error:
sc = yt.create_scene(ds)
cam = sc.camera
cam.focus = [0, 0, 0]
cam_pos = [1, 0, 0]
north_vector = [0, 1, 0]
cam_pos = [0, 1, 0]
north_vector = [0, 0, 1]
Clearly, the user is specifying cam_pos and north_vector that are **not** aligned.
However, in the current code set-up, position's fget() passes north_vector=None to
`switch_orientation`. Because `north_vector` is None in `switch_orientation`, the old
value of north_vector is passed to `_setup_normalized_vectors` which then errors out
because the new camera position-focus vector is aligned with the old north_vector.
This issue will only arise in rare cases; however, it took me a very perplexed hour (and
learning about python properties :-)) to figure out what was going on.