This code duplicated the code in setup_realm_internal_bots, with some
added logic to avoid trying to create the same bot twice. That logic
was buggy so that it would never work at all -- it subtracted a set of
UserProfile objects from a set of email strings -- so it looked like
the command might blow up when run after the users already existed.
In fact, the buggy logic wasn't necessary, because the work the
command does after it is idempotent -- in particular `create_users`,
within its subroutine `bulk_create_users`, already filters out users
that already exist. So just cut the buggy stuff out, deduplicate the
rest with `setup_realm_internal_bots`, and document that invariant on
the latter.
While we're here, in the common case bail early without doing any
per-realm work in Python, since we're running this on every upgrade.
Aditya Bansal
Greg Price