[jhbuild] Only set DBUS_SYSTEM_BUS_ADDRESS if it's unset

[Frederic Peters <fpeters src gnome org>]

commit 0a43f34e26cf059a5d9512256ab9da7ea4f4b208
Author: Frédéric Péters <fpeters 0d be>
Date:   Thu Mar 31 16:41:33 2011 +0530

    Only set DBUS_SYSTEM_BUS_ADDRESS if it's unset

 jhbuild/config.py |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/jhbuild/config.py b/jhbuild/config.py
index 79f29d1..4e093c4 100644
--- a/jhbuild/config.py
+++ b/jhbuild/config.py
@@ -296,9 +296,10 @@ class Config:
 
         os.environ['UNMANGLED_LD_LIBRARY_PATH'] = os.environ.get('LD_LIBRARY_PATH', '')
 
-        # Use the distribution's D-Bus for the system bus. JHBuild's D-Bus will
-        # be used for the session bus
-        os.environ['DBUS_SYSTEM_BUS_ADDRESS'] = 'unix:path=/var/run/dbus/system_bus_socket'
+        if not os.environ.get('DBUS_SYSTEM_BUS_ADDRESS'):
+            # Use the distribution's D-Bus for the system bus. JHBuild's D-Bus
+            # will # be used for the session bus
+            os.environ['DBUS_SYSTEM_BUS_ADDRESS'] = 'unix:path=/var/run/dbus/system_bus_socket'
 
         # LD_LIBRARY_PATH
         if self.use_lib64: