Running ./manage.py with no arguments and DEBUG enabled causes a stack trace:

$ ./manage.py
Traceback (most recent call last):
  File "./manage.py", line 82, in <module>
    if sys.argv[1] == 'runserver' or sys.argv[1] == 'test':
IndexError: list index out of range

This patch adds a check for the length of argv.

Ran ./manage.py with and without arguments.