OpenVPN with network-manager fails due to "get_secrets_cb(): Failed to request VPN secrets #2: (6) No agents were available for this request."

[Karl-Philipp Richter]

Error message can be spotted in `/var/log`syslog` (there's no other feedback for the user!). Connection worked fine some weeks ago.

expired report about the same issue in Fedora 19: https://bugzilla.redhat.com/show_bug.cgi?id=991650
upstream report: https://bugzilla.gnome.org/show_bug.cgi?id=727621

The mentioned workaround to deactivate password storage and switch the password type to ~"ask always" doesn't work because the same issue occurs.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: network-manager-openvpn-gnome 0.9.10.0-1ubuntu1
Uname: Linux 4.1.4-040104-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Aug 5 13:00:45 2015
InstallationDate: Installed on 2015-06-08 (57 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: network-manager-openvpn
UpgradeStatus: Upgraded to vivid on 2015-06-09 (57 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.