Do not load .dsc to check if an upload is sourceful.

This caused an error when rejecting an upload with an invalid .dsc.

We also do not want to load the .dsc before we have made sure it matches the
hash from the .changes.

dak/process_upload.py

@@ -243,7 +243,7 @@ def get_processed_upload(upload):
 
     pu.changes = open(upload.changes.path, 'r').read()
     pu.changes_filename = upload.changes.filename
-    pu.sourceful = upload.changes.source is not None
+    pu.sourceful = upload.changes.sourceful
     pu.source = control.get('Source')
     pu.version = control.get('Version')
     pu.architecture = control.get('Architecture')

daklib/upload.py

@@ -296,6 +296,13 @@ class Changes(object):
                 self._source = Source(self.directory, source_files, self._keyrings, self._require_signature)
         return self._source
 
+    @property
+    def sourceful(self):
+        """C{True} if the upload includes source
+        @type: bool
+        """
+        return "source" in self.architectures
+
     @property
     def source_name(self):
         """source package name