Merge commit 'mhy/sqlalchemy' into merge

Merge commit 'mhy/sqlalchemy' into merge

* commit 'mhy/sqlalchemy': (135 commits)
  pass session to get_id
  NULL is None, not ""
  fix bad merge in 1c35448b880358d020e81339657e3435fdda9434
  typo fixes
  clean up holding path
  only look in queues which exist
  handle bad checksum lines
  misc fixes
  fix typo
  fix typo
  attempt to ensure we clear up sessions
  make sure we close sessions
  miscellaneous fixups from testing
  convert check_overrides to new DB API
  convert override.py to new DB API
  convert (badly) rm to new DB API
  convert ls to new DB API
  bug fix
  convert import_keyring to new DB API
  convert cruft_report to new DB API
  ...

Signed-off-by: Joerg Jaspert <joerg@debian.org>