Compare two snapshots:
		- return a list of new packages in this snapshot
		- return a list of new builds in this snapshot

		:param snapshot: distribution snapshot
		:type  snapshot: DistributionSnapshot

def compare(self, snapshot):
		"""Compare two snapshots:
		- return a list of new packages in this snapshot
		- return a list of new builds in this snapshot

		:param snapshot: distribution snapshot
		:type  snapshot: DistributionSnapshot
		"""
		builds = snapshot.builds()

		diff_snapshot = DistributionSnapshot(self.distribution(), self.go_version)

		for package in list(set(self._builds.keys()) - set(builds.keys())):
			diff_snapshot.setRpms(package, self._builds[package]["build"], self._builds[package]["build_ts"], self._builds[package]["rpms"])

		for package in list(set(self._builds.keys()) & set(builds.keys())):
			if self._builds[package]["build"] != builds[package]["build"]:
				diff_snapshot.setRpms(package, self._builds[package]["build"], self._builds[package]["build_ts"], self._builds[package]["rpms"])

		# Assuming no package get ever removed (even if retired)
		return diff_snapshot