_pretty_needs_read_lock breaks symbol_versioning.deprecated_passed

Running lp:udd's import_package.py locally to test something with bzrlib from lp:bzr I just got this traceback:

Traceback (most recent call last):
  File "./import_package.py", line 1095, in <module>
    persistent_download_cache=options.persistent_download_cache))
  File "./import_package.py", line 999, in main
    revid_db, bstore, possible_transports=possible_transports)
  File "./import_package.py", line 639, in find_unimported_versions
    possible_transports=possible_transports)
  File "./icommon.py", line 1339, in get_branch
    possible_transports=possible_transports, readonly=readonly)
  File "./icommon.py", line 1503, in get_branch_parts
    dir = br_from.bzrdir.sprout(local_location)
  File "/home/andrew/code/bzr/bzrlib/controldir.py", line 375, in sprout
    create_tree_if_local=create_tree_if_local)
  File "/home/andrew/code/bzr/bzrlib/cleanup.py", line 131, in run
    self.cleanups, self.func, self, *args, **kwargs)
  File "/home/andrew/code/bzr/bzrlib/cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/home/andrew/code/bzr/bzrlib/controldir.py", line 415, in _sprout
    fetch_spec = fetch_spec_factory.make_fetch_spec()
  File "/home/andrew/code/bzr/bzrlib/fetch.py", line 414, in make_fetch_spec
    required_ids=heads_to_fetch, if_present_ids=tags_to_fetch
  File "/home/andrew/code/bzr/bzrlib/graph.py", line 1872, in execute
    if_present_ids=self.if_present_ids, find_ghosts=self.find_ghosts)
  File "<string>", line 4, in search_missing_revision_ids_read_locked
  File "/home/andrew/code/bzr/bzrlib/repository.py", line 1615, in search_missing_revision_ids
    'revision_ids is mutually exclusive with revision_id')
AssertionError: revision_ids is mutually exclusive with revision_id

It turns out that this is because search_missing_revision_ids 'revision_id=symbol_versioning.DEPRECATED_PARAMETER' in its params, and checks for that by calling symbol_versioning.deprecated_passed. That function uses the 'is' operator against the string constant, but the _pretty_needs_read_lock decorator rewrites that param as a literal, breaking that test.

This doesn't affect the 'bzr' tool, but will break other tools that use bzrlib without enabling the fast decorators (i.e. most of them).