ValueError when $SHELL is not an absolute path.

[cedws]

Originally filed as rust-lang/rust-enhanced#391.

When the user's $SHELL is not an absolute path (for example, zsh and not /bin/zsh), the call to rsplit() on line 44 below will throw a ValueError. This is because the $SHELL string contains no slashes.

shellenv/all/shellenv/_posix.py

Lines 42 to 46 in 63ec866

	if shell is None:
	shell = get_user_login_shell()
	_, shell_name = shell.rsplit('/', 1)
	output_type = 'bytes' if sys.version_info < (3,) and for_subprocess else 'unicode'