Call pip to install the templates.

def InstallTemplatePackage():
  """Call pip to install the templates."""
  virtualenv_bin = os.path.dirname(sys.executable)
  extension = os.path.splitext(sys.executable)[1]
  pip = "%s/pip%s" % (virtualenv_bin, extension)

  # Install the GRR server component to satisfy the dependency below.
  major_minor_version = ".".join(
      pkg_resources.get_distribution("grr-response-core").version.split(".")
      [0:2])
  # Note that this version spec requires a recent version of pip
  subprocess.check_call([
      sys.executable, pip, "install", "--upgrade", "-f",
      "https://storage.googleapis.com/releases.grr-response.com/index.html",
      "grr-response-templates==%s.*" % major_minor_version
  ])