Drop method sleep_for_seconds

Method `sleep_for_seconds` is used in only one place. It causes the current
thread to sleep for somewhere between N to N + 1 seconds, inclusive, and this
behaviour seems to serve no purpose where it is used. Drop the method and just
call `time.sleep` as needed instead.
Merge pull request #1598 from Ichimonji10/cli-refactor

Drop method sleep_for_seconds