In python 3, subprocess uses bytes for input and output if
universal_newlines=False (the default). It uses str for input and
output if universal_newlines=True.
Since we're dealing with strings here, add universal_newlines=True
to subprocess.check_output calls.
This is important for both ensuring the Nagios checks work correctly
in production, as well as making sure the `zulip` user can access the
virtualenv (owned by the `travis` user) in Travis CI.
Apparently, c74a74dc74 introduced a bug
where we are no longer correctly depending on build-essential as part
of the Zulip development environment installation process.
Fixes#1111.
This is needed because hash_reqs.py is used to create a virtualenv.
Currently we only use virtualenv in development, but we will soon
start using it in production. Scripts used in production should be
put in scripts/.
Eklavya Sharma
Tim Abbott