Remove `from __future__ import absolute_import`.

Except in:
- docs/writing-bots-guide.md, because bots are supposed to be Python 2
  compatible
- puppet/zulip_ops/files/zulip-ec2-configure-interfaces, because this
  script is still on python2.7
- tools/lint
- tools/linter_lib
- tools/lister.py

For the latter two, because they might be yanked away to a separate repo
for general use with other FLOSS projects.

analytics/lib/fixtures.py

@@ -1,4 +1,4 @@
-from __future__ import division, absolute_import
+from __future__ import division
 
 from zerver.models import Realm, UserProfile, Stream, Message
 from analytics.models import InstallationCount, RealmCount, UserCount, StreamCount

confirmation/models.py

@@ -2,8 +2,6 @@
 
 # Copyright: (c) 2008, Jarek Zgoda <jarek.zgoda@gmail.com>
 
-from __future__ import absolute_import
-
 __revision__ = '$Id: models.py 28 2009-10-22 15:03:02Z jarek.zgoda $'
 
 import datetime

docs/webhook-walkthrough.md

@@ -58,7 +58,6 @@ python file, `zerver/webhooks/mywebhook/view.py`.
 The Hello World integration is in `zerver/webhooks/helloworld/view.py`:
 
 ```
-from __future__ import absolute_import
 from django.utils.translation import ugettext as _
 from zerver.lib.actions import check_send_stream_message
 from zerver.lib.response import json_success, json_error

manage.py

@@ -1,6 +1,4 @@
 #!/usr/bin/env python3
-from __future__ import absolute_import
-
 import os
 import sys
 

scripts/get-django-setting

@@ -1,6 +1,4 @@
 #!/usr/bin/env python3
-from __future__ import absolute_import
-
 import os
 import sys
 

scripts/lib/email-mirror-postfix

@@ -37,7 +37,6 @@ Also you can use optional keys to configure the script and change default values
 
 -t                  Disable sending request to the Zulip server. Default value: False.
 """
-from __future__ import absolute_import
 
 import os
 import ssl

static/assets/favicon/generate

@@ -1,5 +1,4 @@
 #!/usr/bin/env python3
-from __future__ import absolute_import
 import xml.etree.ElementTree as ET
 import subprocess
 from six.moves import range

tools/linter_lib/printer.py

@@ -1,4 +1,5 @@
-from __future__ import print_function, absolute_import
+from __future__ import print_function
+from __future__ import absolute_import
 
 import sys
 import os