Existing repositories cause clone to fail

Cloning package traits
URL: https://github.com/enthought/traits.git
fatal: destination path 'traits' already exists and is not an empty directory.
Traceback (most recent call last):
File "ets/ets.py", line 149, in
main()
File "ets/ets.py", line 136, in main
subprocess.check_call(['git', 'clone', pkg_url, ets_pkg_name])
File "/home/jwiggins/epd-6.3/lib/python2.6/subprocess.py", line 488, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['git', 'clone', 'https://github.com/enthought/traits.git', 'traits']' returned non-zero exit status 128

Perhaps it should just print the error and continue on its merry way?