Often I work around this problem by calculating the condition in an own statement:
condition = (collResv.repeatability is None or
collResv.somethingElse)
if condition:
collResv.rejected = True
collResv.rejectCompletely()
Though, for a still relatively short condition as in your specific example I’d go for nosklo‘s solution – the extra statement used here is more suited for even longer conditional expressions.