le error

le exits with a error if started without arguments or if not enough arguments are given.
It would be more intuitive for users if this tool would follow the conventions of ls.

Traceback (most recent call last):
  File "/klausurarchiv/bin/le", line 258, in <module>
    nLectures=max([len(v.scheme.lectures) for v in exams])
ValueError: max() arg is an empty sequence