This keeps the examples in line with our actual codebase.
Also while I'm here revise it to explain the actual motivation for our
use of `env`, and to correct some subtle details -- it's actually the
kernel that interprets the shebang (as visible in e.g. a `strace` log),
not the shell, and when the program is executed as `./my_program.py`
the exact name including `./` is passed to the interpreter.
This causes `upgrade-zulip-from-git`, as well as a no-option run of
`tools/build-release-tarball`, to produce a Zulip install running
Python 3, rather than Python 2. In particular this means that the
virtualenv we create, in which all application code runs, is Python 3.
One shebang line, on `zulip-ec2-configure-interfaces`, explicitly
keeps Python 2, and at least one external ops script, `wal-e`, also
still runs on Python 2. See discussion on the respective previous
commits that made those explicit. There may also be some other
third-party scripts we use, outside of this source tree and running
outside our virtualenv, that still run on Python 2.
This works fine in my testing -- I followed it on a fresh `trusty` VM,
after just getting SSL certs with our LetsEncrypt instructions, and
the install completed successfully.
And in the source tree, the only evidence I can find of a potential
remaining dependency on the `/root/zulip` path is the Nagios config in
`puppet/zulip_ops/`. That's actually already broken, in that it
depends on `/root/zulip/api/`, so we'll have to sort that out;
and in any case, it doesn't matter to most people installing Zulip.
Add a mention that the install script will move the just-unpacked
directory out from under you. While we're here, add a few words about
where the deployed code is laid out.
Text of those last words tweaked by tabbott.
This follows up on 207cf6302 from last year to clean up cases that
have apparently popped up since then. Invoking the scripts directly
makes a cleaner command line in any case, and moreover is essential
to how we control running a Zulip install as either Python 2 or 3
(soon, how we always ensure it runs as Python 3.)
One exception: we're currently forcing `provision` in dev to run
Python 3, while still running both Python 2 and Python 3 jobs in CI.
We use a non-shebang invocation to do the forcing of Python 3.
