Comment 8 for bug 1750917

Reviewed: https://review.openstack.org/553592
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=ccdf2d976f4d26df4f6a2a915da6ff0f643757ac
Submitter: Zuul
Branch: master

commit ccdf2d976f4d26df4f6a2a915da6ff0f643757ac
Author: Lance Bragstad <email address hidden>
Date: Thu Mar 15 19:39:43 2018 +0000

    Add logging for xmlsec1 installation

    Keystone uses a library called xmlsec1 to create SAML assertions when
    acting as an identity provider. If this library isn't present and
    someone attempts to authenticate, keystone will throw an HTTP 500.
    The only thing the error says is that a file or directory doesn't
    exist.

    This patch uses subprocess to check if the provided binary actually
    exists on the system and handles cases when it isn't and logs a
    useful message for operators.

    Change-Id: I41cf87702df5389c1424d35f0abcef9c16301450
    Closes-Bug: 1750917