Now the kitten passes its script to /bin/sh and detects the login shell
using various strategies based on the value of $USER on the remote
machine. The strategies are tried one after another till one succeeds:
1) getent passwd $USER
2) id -P
3) python pwd module
4) parsing /etc/passwd
The hope is that these strategies will fail on fewer systems than
relying on the login shell being POSIX compliant.
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