title: Why cannot call method in org.freedesktop.NetworkManager with dbus in Python?
body: <p>I tried the code below in interactive python shell and got the follow error in line 3 of code, using D-Feet I see that path and interface exists in bus, and with the command dbus-send I able to get the devices, see in end of this message. Why not work with this code in python? PS: I using ubuntu 12.04, tried too in ubuntu 11, same problem.</p>
  
  <p>Code:</p>
  
  <pre><code>import dbus
  bus = dbus.SessionBus()
  obj = bus.get_object('org.freedesktop.NetworkManager', '/org/freedesktop/NetworkManager')
  t = dbus.Interface(obj, "org.freedesktop.NetworkManager")
  t.GetDevices()
  </code></pre>
  
  <p>Output error entering line 3 of code:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;input&gt;", line 1, in &lt;module&gt;
    File "/usr/lib/pymodules/python2.7/dbus/bus.py", line 244, in get_object
      follow_name_owner_changes=follow_name_owner_changes)
    File "/usr/lib/pymodules/python2.7/dbus/proxies.py", line 241, in __init__
      self._named_service = conn.activate_name_owner(bus_name)
    File "/usr/lib/pymodules/python2.7/dbus/bus.py", line 183, in activate_name_owner
      self.start_service_by_name(bus_name)
    File "/usr/lib/pymodules/python2.7/dbus/bus.py", line 281, in start_service_by_name
      'su', (bus_name, flags)))
    File "/usr/lib/pymodules/python2.7/dbus/connection.py", line 630, in call_blocking
      message, timeout)
  DBusException: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.NetworkManager was not provided
   by any .service files
  </code></pre>
  
  <p>Shell command that work:</p>
  
  <pre><code>dbus-send --system --print-reply --reply-timeout=2000 --type=method_call --dest=org.freedesktop.NetworkManager /org/freedesktop/NetworkManager org.freedesktop.NetworkManager.GetDevices
  </code></pre>
  
  <p>Output:</p>
  
  <pre><code>method return sender=:1.2 -&gt; dest=:1.69 reply_serial=2
     array [
        object path "/org/freedesktop/NetworkManager/Devices/0"
     ]
  </code></pre>
  
  <p>This is just a example, I wish to know why don't work, If I change line 3 to (note the DBus name in first parameter): </p>
  
  <pre><code>obj = bus.get_object('org.freedesktop.DBus', '/org/freedesktop/NetworkManager')
  </code></pre>
  
  <p>the error don't occur, but in this interface the method GetDevices doesn't exists.</p>