=== modified file 'smart/channels/apt_deb.py'
--- smart/channels/apt_deb.py	2010-07-02 13:19:08 +0000
+++ smart/channels/apt_deb.py	2010-07-18 15:13:32 +0000
@@ -118,6 +118,7 @@
             badsig = False
             goodsig = False
             validsig = None
+            signature = None
             for line in output.splitlines():
                 if line.startswith("[GNUPG:]"):
                     tokens = line[8:].split()
@@ -126,13 +127,16 @@
                         validsig = tokens[1]
                     elif first == "GOODSIG":
                         goodsig = True
+                        signature = tokens[1]
+                    elif first == "NO_PUBKEY":
+                        signature = tokens[1]
                     elif first == "BADSIG":
                         badsig = True
             if badsig:
                 raise Error, _("Channel '%s' has bad signature") % self
             if (not goodsig or
                 (self._fingerprint and validsig != self._fingerprint)):
-                raise Error, _("Channel '%s' signed with unknown key") % self
+                raise Error, _("Channel '%s' signed with unknown key %s") % (self, signature[-8:])
 
     def _parseRelease(self, release_item):
         checksum = {}

=== modified file 'tests/aptdeb.py'
--- tests/aptdeb.py	2010-04-15 10:30:34 +0000
+++ tests/aptdeb.py	2010-07-18 15:07:46 +0000
@@ -14,6 +14,7 @@
 from tests import TESTDATADIR
 
 
+ID = "66643A0C"
 FINGERPRINT = "2AAC 7928 0FBF 0299 5EB5  60E2 2253 B29A 6664 3A0C"
 
 
@@ -107,7 +108,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")
 
@@ -123,7 +124,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")
 
@@ -139,7 +140,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")
 
@@ -154,7 +155,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")
 
@@ -170,7 +171,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")
 
@@ -185,7 +186,7 @@
             self.check_channel(channel)
         except Error, error:
             self.assertEquals(str(error),
-                              "Channel 'alias' signed with unknown key")
+                              "Channel 'alias' signed with unknown key %s" % ID)
         else:
             self.fail("Fetch worked with a bad signature! :-(")