Revert "Use apt-add-repository to setup Zulip PPA."

This reverts commit 3f95e567c1.

Apparently `apt-add-repository` fails periodically in CI.  I suspect
this is some sort of silly networking problem, but given that all
we're saving is a few lines of code, the old version was better if
this fails basically ever.

scripts/lib/install

@@ -15,8 +15,8 @@ DEPLOYMENT_TYPE="${DEPLOYMENT_TYPE:-voyager}"
 PUPPET_CLASSES="${PUPPET_CLASSES:-zulip::voyager}"
 VIRTUALENV_NEEDED="${VIRTUALENV_NEEDED:-yes}"
 
-# Add the Zulip PPA
-apt-add-repository --enable-source --yes ppa:tabbott/zulip
+/root/zulip/scripts/lib/setup-apt-repo
+
 apt-get update
 apt-get -y dist-upgrade $APT_OPTIONS
 apt-get install -y puppet git python python-six crudini $ADDITIONAL_PACKAGES

scripts/lib/setup-apt-repo

@@ -0,0 +1,18 @@
+#!/bin/bash
+set -x
+set -x
+
+apt-get install -y lsb-release
+
+# First, install any updates from the apt repo that may be needed
+wget -qO - https://zulip.com/dist/keys/zulip-ppa.asc | apt-key add -
+release=$(lsb_release -sc)
+if [ "$release" = "trusty" ] || [ "$release" = "xenial" ]; then
+    cat >/etc/apt/sources.list.d/zulip.list <<EOF
+deb http://ppa.launchpad.net/tabbott/zulip/ubuntu $release main
+deb-src http://ppa.launchpad.net/tabbott/zulip/ubuntu $release main
+EOF
+else
+    echo "Unsupported release $release."
+    exit 1
+fi

tools/provision.py

@@ -159,8 +159,7 @@ def main():
     # project.
     os.chdir(ZULIP_PATH)
 
-    # Add the Zulip PPA and install apt dependencies
-    run(["sudo", "apt-add-repository", "--enable-source", "--yes", "ppa:tabbott/zulip"])
+    run(["sudo", "./scripts/lib/setup-apt-repo"])
     run(["sudo", "apt-get", "update"])
     run(["sudo", "apt-get", "-y", "install", "--no-install-recommends"] + APT_DEPENDENCIES[codename])