<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def repo_def_matches_reality(juicer_def, pulp_def):
 """Compare a juicer repo def with a given pulp definition. Compute and return the update necessary to make `pulp_def` match `juicer_def`. `juicer_def` - A JuicerRepo() object representing a juicer repository `pulp_def` - A PulpRepo() object representing a pulp repository """

    return juicer.common.Repo.RepoDiff(juicer_repo=juicer_def, pulp_repo=pulp_def)