convert: have debugsvnlog obtain standard streams from ui

This will help porting to Python 3, where sys.stdin/out/err are unfortunately
unicode streams so we can't use them directly.

hgext/convert/subversion.py

@@ -5,7 +5,6 b' from __future__ import absolute_import'
 
 import os
 import re
-import sys
 import tempfile
 import xml.dom.minidom
 
@@ -164,8 +163,8 b' def debugsvnlog(ui, **opts):'
         raise error.Abort(_('debugsvnlog could not load Subversion python '
                            'bindings'))
 
-    args = decodeargs(sys.stdin.read())
-    get_log_child(sys.stdout, *args)
+    args = decodeargs(ui.fin.read())
+    get_log_child(ui.fout, *args)
 
 class logstream(object):
     """Interruptible revision log iterator."""