Loading camera model is broken with scipy version 1.6.x

[yangyushi]

When loading the intrinsic parameters to calibrate the camera, I get the following error

Traceback (most recent call last):
  File "calibration.py", line 39, in <module>
    cam.read_int(config[cam_name]['intrinsic'])
  File "/home/yy17363/Code/FishPy/lib/fish_3d/camera.py", line 237, in read_int
    cam = pickle.load(f)
  File "rotation.pyx", line 537, in scipy.spatial.transform.rotation.Rotation.__setstate__
AttributeError: 'str' object has no attribute 'copy'

This might relate to this issue.

Picking the object for repeated use is simply not a good idea. I think the way to solve the issue is, ultimately, dump the camera parameters as text files like json.

A temporary fix would be using scipy 1.5.x