This module caused 500 error with no logs on site migration

I just migrated one of my sites to a new server (standard git pull of the code, and db import from sql dump). On visiting the site on the new server, I got a dreaded 500 error on every page (close to wsod, but with error message)... with no logs in watchdog, or error logs for php, apache, mysql, or varnish. Just... nothing. drush status said drupal was bootstrapping, and everything was fine.

I spent the better part of two days troubleshooting this... was this an Apache configuration issue? Varnish? Cloudflare? DB corruption? File permissions? What was going on?

Eventually I narrowed down the issue to *something* in the db, but apparently not a corruption (since I was able to pull in the same db fine on my dev server). I resorted to disabling modules via drush in clusters... and finally narrowed the issue down to one module: composer_manager. Disabled that one module (and the one module that was depending on it--sparkpost), and everything worked like a charm.

Since I was pulling everything in via git, obviously the module had not been "set up" on the new server. Apparently this killed everything, without leaving a single log message of any kind in its wake.