Steps to reproduce:

1. (Re-)mount /proc with hidepid=1 (or =2)
2. Restart nm-applet

nm-applet's icon does not reappear after the restart. This used to work with version 1.0.

Originally reported at:
  https://bugs.launchpad.net/bugs/1568829

Since I upgraded to -proposed network-manager and network-manager-gnome versions, nm-applet no longer works.
Manually starting it on a console give:

$ nm-applet 

(nm-applet:6250): nm-applet-WARNING **: GDBus.Error:org.freedesktop.NetworkManager.AgentManager.PermissionDenied: Unable to determine request sender and UID.
(nm-applet:6250): libnm-CRITICAL **: nm_client_get_nm_running: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_get_state: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_networking_get_enabled: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_wireless_get_enabled: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_wireless_hardware_get_enabled: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_wwan_get_enabled: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_wwan_hardware_get_enabled: assertion 'NM_IS_CLIENT (client)' failed
(nm-applet:6250): libnm-CRITICAL **: nm_client_get_devices: assertion 'NM_IS_CLIENT (client)' failed


What's odd is the NM and NM-gnome base versions are not identical:

$ apt-cache policy network-manager network-manager-gnome
network-manager:
  Installed: 1.1.93-0ubuntu1
  Candidate: 1.1.93-0ubuntu1
  Version table:
 *** 1.1.93-0ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1.0.4-0ubuntu10 500
        500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages
network-manager-gnome:
  Installed: 1.1.93-1ubuntu1
  Candidate: 1.1.93-1ubuntu1
  Version table:
 *** 1.1.93-1ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     1.0.10-1ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: network-manager-gnome 1.1.93-1ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-18.34-generic 4.4.6
Uname: Linux 4.4.0-18-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Mon Apr 11 08:16:59 2016
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
 WimaxEnabled=true
RfKill:
 0: phy0: Wireless LAN
 	Soft blocked: no
 	Hard blocked: no
SourcePackage: network-manager-applet
UpgradeStatus: No upgrade log present (probably fresh install)
nmcli-con:
 Error: command ['nmcli', '-f', 'all', 'con'] failed with exit code 1: 
 (process:7301): nmcli-CRITICAL **: Error: Could not create NMClient object: Unable to authenticate request..
nmcli-dev:
 Error: command ['nmcli', '-f', 'all', 'dev'] failed with exit code 1: 
 (process:7297): nmcli-CRITICAL **: Error: Could not create NMClient object: Unable to authenticate request..
nmcli-nm: Error: command ['nmcli', '-f', 'all', 'nm'] failed with exit code 2: Error: Object 'nm' is unknown, try 'nmcli help'.