[tests] Stop counting pickle bytes in ResultSet tests Between python 2's pickle and cPickle implementations, the various protocol versions added in python 3, the length of the pickled string is completely unpredictable. Instead, do a simple round trip and test a few attributes.

Pygments
#fyzz XXX pip install fails
cubicweb-card
cubicweb-file
cubicweb-localperms
cubicweb-tag