error message "error queue: 140B0009: error:140B0009:SSL routines:SSL_CTX_use_PrivateKey_file:PEM lib" is unhelpful

[Karl-Philipp Richter]

The error message "error queue: 140B0009: error:140B0009:SSL routines:SSL_CTX_use_PrivateKey_file:PEM lib" is unhelpful. Please replace it with a message which explain which error occured for what reason and what are possible steps to take to fix the error.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: stunnel4 3:5.35-1
Uname: Linux 4.8.0-040800-generic x86_64
NonfreeKernelModules: openafs
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
Date: Sun Oct 23 00:24:29 2016
InstallationDate: Installed on 2015-04-20 (551 days ago)
InstallationMedia: Ubuntu-Server 14.10 "Utopic Unicorn" - Release amd64 (20141022.2)
ProcEnviron:
 TERM=screen.xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: stunnel4
UpgradeStatus: Upgraded to yakkety on 2016-10-19 (3 days ago)