Merge commit '837293c31' into anoa/dinsic_release_1_21_x

* commit '837293c31':
  Remove obsolete __future__ imports (#8337)
  Use admin_patterns for all admin APIs. (#8331)
  Fix a potential bug of UnboundLocalError (#8329)
  Switch metaclass initialization to python 3-compatible syntax (#8326)
  Catch-up after Federation Outage (split, 4): catch-up loop (#8272)
  Use slots in attrs classes where possible (#8296)
  Fix typos in comments.
  Add the topic and avatar to the room details admin API (#8305)
  Improve SAML error messages (#8248)
  Add experimental support for sharding event persister. Again. (#8294)
  Make `StreamToken.room_key` be a `RoomStreamToken` instance. (#8281)
  Use TLSv1.2 for fake servers in tests (#8208)
  Add /_synapse/client to the reverse proxy docs (#8227)
  Clean up `Notifier.on_new_room_event` code path (#8288)

scripts/move_remote_media_to_new_store.py

@@ -32,8 +32,6 @@ To use, pipe the above into::
     PYTHON_PATH=. ./scripts/move_remote_media_to_new_store.py <source repo> <dest repo>
 """
 
-from __future__ import print_function
-
 import argparse
 import logging
 import os

scripts/register_new_matrix_user

@@ -14,8 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import print_function
-
 from synapse._scripts.register_new_matrix_user import main
 
 if __name__ == "__main__":