Apparently whitespaces are not allowed in a class expression.

cf-promises fails with:

/var/cfengine/masterfiles/def.cf:185:111: error: Context string is invalid/out of range
      "postgresql_maintenance_supported" expression => "policy_server.enterprise.!(cfengine_3_4| cfengine_3_5)";

This appears too strict but disabling for now to let the buildsystem continue with package building.
Redmine #5763: Do not create a zero sized file if src does not exist.

(cherry picked from commit 5a9f8df167ebae77d2e60069f23514c6e113170a)

Conflicts:
	lib/3.7/files.cf