@mpm: it works with your patch. The test output is slightly modified into:
"""
ERROR: /Users/pmezard/dev/mercurial/hg/hg-pmezard/tests/test-rebase-copies
output changed
--- /Users/pmezard/dev/mercurial/hg/hg-pmezard/tests/test-rebase-copies.out 
+++ /Users/pmezard/dev/mercurial/hg/hg-pmezard/tests/test-rebase-copies.err 
@@ -4,6 +4,7 @@
 1 files updated, 0 files merged, 1 files removed, 0 files unresolved
 created new head
 1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+merging dd/a
  local changed dd/a which remote deleted
 use (c)hanged version or (d)elete? c
 adding branch
!
Failed test-rebase-copies: output changed
# Ran 1 tests, 0 skipped, 1 failed.
"""
but that's probably better anyway.