Failure to slew_to_target does not raise a PanError

[danjampro]

The current behaviour of POCS is to log a warning message if the slew is not possible. This can obviously lead to a lot of problems down the line if not handled properly. This problem exists for the bisque mount as well as in the abstract mount class.

Suggest raising a PanError if the slew fails.

Code :

POCS/src/panoptes/pocs/mount/bisque.py

Line 186 in e6df64b

self.logger.warning(f"Problem slewing to mount coordinates: {mount_coords} {e}")