Display errors from setting up temporary files in Init()

[pjcdawkins]

Prints a clear error message instead of silently failing:

$ go run ./cmd/platform/main.go help | head -n1
Command: help
$
$ platform help | head -n1
Command: help
$
$ chmod u-x /tmp/platform*
$
$ platform help | head -n1
$
$ go run ./cmd/platform/main.go help | head -n1
2024/12/05 16:28:53 could not acquire lock: open /tmp/platformsh-cli-0.0.0-0.0.0/.lock: permission denied
exit status 1

[akalipetis]

LGTM