Add way how to support signature to dbus call

- If dbus method is called with empty array as an argument then
dbus is not able to determine type of arguments and throws Error
- This commit adds way how to add it in such case

Author: TomasKorbar

authconn.py

@@ -233,6 +233,10 @@ def _make_binding (self, fname, fn):
 
     def _authloop (self, fname, fn, *args, **kwds):
         self._passes = 0
+        # remove signature if dbus is not being used and signature is provided
+        if not self._using_polkit():
+            kwds.pop('signature', None)
+
         c = self._connection
         retry = False
         while True:

cupspk.py

@@ -99,6 +99,8 @@ def _get_cups_pk(self):
 
     def _call_with_pk_and_fallback(self, use_fallback, pk_function_name, pk_args, fallback_function, *args, **kwds):
         pk_function = None
+        # take signature from kwds if is provided
+        dbus_args_signature = kwds.pop('signature', None)
 
         if not use_fallback:
             cups_pk = self._get_cups_pk()
@@ -116,7 +118,7 @@ def _call_with_pk_and_fallback(self, use_fallback, pk_function_name, pk_args, fa
         while True:
             try:
                 # FIXME: async call or not?
-                pk_retval = pk_function(*pk_args)
+                pk_retval = pk_function(*pk_args, signature = dbus_args_signature)
 
                 # if the PK call has more than one return values, we pop the
                 # first one as the error message

troubleshoot/DeviceListed.py

@@ -86,6 +86,7 @@ def display (self):
             self.authconn = answers['_authenticated_connection']
             try:
                 self.op = TimedOperation (self.authconn.getDevices,
+                                          kwargs={'signature': 'iiasas'},
                                           parent=parent)
                 devices = self.op.run ()
                 devices_list = []