python: make dbus, gi examples, and debug-helper.py python3 ready

https://bugzilla.gnome.org/show_bug.cgi?id=791121

examples/python/gi/list-connections.py

@@ -27,7 +27,7 @@ from gi.repository import NM
 # This example asks settings service for all configured connections.
 
 def print_values(setting, key, value, flags, data):
-    print "  %s.%s: %s" % (setting.get_name(), key, value)
+    print("  %s.%s: %s" % (setting.get_name(), key, value))
 
 if __name__ == "__main__":
     # create Client object
@@ -38,7 +38,7 @@ if __name__ == "__main__":
 
     # print the connections' details
     for c in connections:
-        print "=== %s : %s ===" % (c.get_id(), c.get_path())
+        print("=== %s : %s ===" % (c.get_id(), c.get_path()))
         c.for_each_setting_value(print_values, None)
-        print "\n"
+        print("\n")