<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_default(cls, name):
 """Replaces the current application default depot"""

        if name not in cls._depots:
            raise RuntimeError('%s depot has not been configured' % (name,))
        cls._default_depot = name