def has_permission(user, proposal, speaker=False, reviewer=False):
"""
Returns whether or not ther user has permission to review this proposal,
with the specified requirements.
If ``speaker`` is ``True`` then the user can be one of the speakers for the
proposal. If ``reviewer`` is ``True`` the speaker can be a part of the
reviewer group.
"""
if user.is_superuser:
return True
if speaker:
if user == proposal.speaker.user or \
proposal.additional_speakers.filter(user=user).exists():
return True
if reviewer:
if user.groups.filter(name="reviewers").exists():
return True
return False