Use venv for base hub environment

- TLJH should support raspberry pi, which runs ARM. conda does
  not support ARM.
- Get nodejs from nodesource instead of conda or default repositories.
  Default repositories get out of date pretty quickly.
- Install CHP from npm

tljh/apt.py

@@ -0,0 +1,43 @@
+"""
+Utilities for working with the apt package manager
+"""
+import os
+import subprocess
+
+
+def trust_gpg_key(key):
+    """
+    Trust given GPG public key.
+
+    key is a GPG public key (bytes) that can be passed to apt-key add via stdin.
+    """
+    subprocess.run(['apt-key', 'add', '-'], input=key, check=True)
+
+
+def add_source(name, source_url, section):
+    """
+    Add a debian package source.
+
+    distro is determined from /etc/os-release
+    """
+    # lsb_release is not installed in most docker images by default
+    distro = subprocess.check_output(['/bin/bash', '-c', 'source /etc/os-release && echo ${VERSION_CODENAME}']).decode().strip()
+    line = f'deb {source_url} {distro} {section}'
+    with open(os.path.join('/etc/apt/sources.list.d/', name + '.list'), 'a+') as f:
+        # Write out deb line only if it already doesn't exist
+        if f.read() != line:
+            f.seek(0)
+            f.write(line)
+            f.truncate()
+            subprocess.check_output(['apt-get', 'update', '--yes'])
+
+
+def install_packages(packages):
+    """
+    Install debian packages
+    """
+    subprocess.check_output([
+        'apt-get',
+        'install',
+        '--yes'
+    ] + packages)