The `with sh.sudo` pattern that we were using in python-sh was
deprecated, and emperically hangs on Ubuntu xenial. Since in general
the use of python-sh/python-pbs caused trouble (requiring extra
dependencies, confusing syntax), this just removes it.
We replace it with a new zulip_tools.py library function that echoes
the command line and streams the output.
We do the same to install-phantomjs so we can remove that dependency.
A common issue when doing a Zulip upgrade is trying to pass
upgrade-zulip a tarball path under /root, which doesn't work because
the Zulip user doesn't have permission to read the tarball. We
could fix this by just unpacking the tarballs as root, but it seemed
like a nicer approach would be to archive the release tarballs
somewhere readable by the Zulip user (/home/zulip/archives) and unpack
them from there.
Fixes#208.
We still need it in integrations, because those don't require Python
2.7, but we don't need it in any of our code that runs on internal
servers.
(imported from commit 3c340567f1a372dcb4206c6af9a6e5e18005b1b8)