Bug#938550: spyder: Python2 removal in sid/bullseye

[Drew Parsons]

Hi Frédéric, I prepared spyder (and spyder-kernels) for python2 removal. 
  The removal of cloudpickle forces us to do it earlier than we otherwise 
might have.

With spyder, it made sense to me to keep spyder as the main binary 
package, relegating spyder3 to a transitional dependency package. I set 
/usr/bin/spyder as a symlink to spyder3 (manpage likewise). Let me know 
if you're happy with that and we can go ahead with the upload.  
Otherwise I can swap it to keep spyder3 as the binary package.

Drew

p.s. lintian is complaining about renaming the MIT licence as expat.