provision: Use NVM to install node and npm.

NVM takes a specific node version and installs the node package and
a corresponding compatible npm package.

We use it in a somewhat hackish way to install node/npm globally with
a pinned version, since that's how we actually want to consume node in
our development environment.

Other details:
- Travis CI now is configured to use the version of node installed by
provision; the easiest way to do this was to sabotage the existing node
installation.
- jsdom is upgraded to a current version, which both requires recent
node and also is required for the tests to pass with recent node.
This fixes running the node tests on Xenial.

Fixes #1498.

[tweaked by tabbott]

tools/provision.py

@@ -25,10 +25,8 @@ SUPPORTED_PLATFORMS = {
     ],
 }
 
-NPM_VERSION = '3.9.3'
 PY2_VENV_PATH = "/srv/zulip-venv"
 PY3_VENV_PATH = "/srv/zulip-py3-venv"
-TRAVIS_NODE_PATH = os.path.join(os.environ['HOME'], 'node')
 VAR_DIR_PATH = os.path.join(ZULIP_PATH, 'var')
 LOG_DIR_PATH = os.path.join(VAR_DIR_PATH, 'log')
 UPLOAD_DIR_PATH = os.path.join(VAR_DIR_PATH, 'uploads')
@@ -81,11 +79,9 @@ UBUNTU_COMMON_APT_DEPENDENCIES = [
     "rabbitmq-server",
     "redis-server",
     "hunspell-en-us",
-    "nodejs",
-    "nodejs-legacy",
     "supervisor",
     "git",
-    "npm",
+    "libssl-dev",
     "yui-compressor",
     "wget",
     "ca-certificates",      # Explicit dependency in case e.g. wget is already installed
@@ -120,29 +116,6 @@ REPO_STOPWORDS_PATH = os.path.join(
 
 LOUD = dict(_out=sys.stdout, _err=sys.stderr)
 
-def install_npm():
-    # type: () -> None
-    if not TRAVIS:
-        if subprocess_text_output(['npm', '--version']) != NPM_VERSION:
-            run(["sudo", "npm", "install", "-g", "npm@{}".format(NPM_VERSION)])
-
-        return
-
-    run(['mkdir', '-p', TRAVIS_NODE_PATH])
-
-    npm_exe = os.path.join(TRAVIS_NODE_PATH, 'bin', 'npm')
-    travis_npm = subprocess_text_output(['which', 'npm'])
-    if os.path.exists(npm_exe):
-        run(['sudo', 'ln', '-sf', npm_exe, travis_npm])
-
-    version = subprocess_text_output(['npm', '--version'])
-    if os.path.exists(npm_exe) and version == NPM_VERSION:
-        print("Using cached npm")
-        return
-
-    run(["npm", "install", "-g", "--prefix", TRAVIS_NODE_PATH, "npm@{}".format(NPM_VERSION)])
-    run(['sudo', 'ln', '-sf', npm_exe, travis_npm])
-
 
 def main():
     # type: () -> int
@@ -224,10 +197,12 @@ def main():
         run(["tools/setup/postgres-init-test-db"])
         run(["tools/do-destroy-rebuild-test-database"])
         run(["python", "./manage.py", "compilemessages"])
-    # Install the pinned version of npm.
-    install_npm()
-    # Run npm install last because it can be flaky, and that way one
-    # only needs to rerun `npm install` to fix the installation.
+
+    # Here we install nvm, node, and npm.
+    run(["sudo", "tools/setup/install-node"])
+
+    # This is a wrapper around `npm install`, which we run last since
+    # it can often fail due to network issues beyond our control.
     try:
         setup_node_modules()
     except subprocess.CalledProcessError: