Update mask inversion inside torch/so3.py

[Ronnypetson]

I recently found two occurrences of this error, both in torch/so3.py:

Traceback (most recent call last):
File "", line 1, in
File "/home/ubuntu/.local/lib/python3.6/site-packages/liegroups/torch/se3.py", line 80, in exp
rot_jac = cls.RotationType.left_jacobian(phi)
File "/home/ubuntu/.local/lib/python3.6/site-packages/liegroups/torch/so3.py", line 187, in left_jacobian
#large_angle_mask = 1 - small_angle_mask # element-wise not
File "/home/ubuntu/anaconda3/envs/pytorch_p36/lib/python3.6/site-packages/torch/tensor.py", line 362, in rsub
return _C._VariableFunctions.rsub(self, other)
RuntimeError: Subtraction, the - operator, with a bool tensor is not supported. If you are trying to invert a mask, use the ~ or logical_not() operator instead.

I could verify locally that it is just a matter of doing what is suggested and it works fine.
P.S.: My pytorch version is 1.3

[leeclemnet]

This should be fixed in master as of 79ec37c.