Merge branch 'master' into ticket_3100

diff --cc doc/build/faq.rst
Simple merge

diff --cc lib/sqlalchemy/orm/mapper.py
Simple merge

diff --cc lib/sqlalchemy/orm/persistence.py
index 1288c910f9fe72b9623f6161061e7b96192b8b8e,28254cc1033866230529c4cd95654d551643dc0f..c4a9402fbc4318740f9dcd0c1f0e4a317d5a58be
--- 1/lib/sqlalchemy/orm/persistence.py
--- 2/lib/sqlalchemy/orm/persistence.py
+++ b/lib/sqlalchemy/orm/persistence.py
@@@ -15,10 -15,10 +15,10 @@@ in unitofwork.py
  """
  
  import operator
 -from itertools import groupby
 +from itertools import groupby, chain
  from .. import sql, util, exc as sa_exc, schema
  from . import attributes, sync, exc as orm_exc, evaluator
- from .base import state_str, _attr_as_key
+ from .base import state_str, _attr_as_key, _entity_descriptor
  from ..sql import expression
  from . import loading
  
@@@ -560,12 -441,12 +560,12 @@@ def _collect_delete_commands(base_mappe
                      state, state_dict, col)
              if value is None:
                  raise orm_exc.FlushError(
-                     "Can't delete from table "
+                     "Can't delete from table %s "
                      "using NULL for primary "
-                     "key value")
+                     "key value on column %s" % (table, col))
  
          if update_version_id is not None and \
 -                table.c.contains_column(mapper.version_id_col):
 +                mapper.version_id_col in mapper._cols_by_table[table]:
              params[mapper.version_id_col.key] = update_version_id
          yield params, connection
  

diff --cc lib/sqlalchemy/orm/session.py
Simple merge

diff --cc test/orm/test_session.py
Simple merge