diff --git a/tools/custom_check.py b/tools/custom_check.py
index 706ceb3c..d4342e6b 100644
--- a/tools/custom_check.py
+++ b/tools/custom_check.py
@@ -166,7 +166,11 @@ def build_custom_checkers(by_lang):
         # and comments which should be rewritten to avoid use of "python2", "python3", etc.
         {'pattern': 'python[23]',
          'exclude': set(['tools/provision']),
+         'include_only': set(['zulip/', 'tools/', 'zulip_botserver/']),
          'description': 'Explicit python invocations should not include a version'},
+        {'pattern': '#!/usr/bin/env python$',
+         'include_only': set(['zulip_bots/']),
+         'description': 'Python shebangs must be python3'},
         {'pattern': '(^|\s)open\s*\(',
          'description': 'open() should not be used in Zulip\'s bots. Use functions'
                         ' provided by the bots framework to access the filesystem.',
diff --git a/zulip_bots/generate_manifest.py b/zulip_bots/generate_manifest.py
index d5a8bce7..cc13eb0a 100755
--- a/zulip_bots/generate_manifest.py
+++ b/zulip_bots/generate_manifest.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import argparse
 import os
diff --git a/zulip_bots/setup.py b/zulip_bots/setup.py
index 03eb9a19..fc070419 100755
--- a/zulip_bots/setup.py
+++ b/zulip_bots/setup.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 from __future__ import print_function
diff --git a/zulip_bots/zulip_bots/bots/chess/test_chess.py b/zulip_bots/zulip_bots/bots/chess/test_chess.py
index 77d1e4b1..840e4f0d 100644
--- a/zulip_bots/zulip_bots/bots/chess/test_chess.py
+++ b/zulip_bots/zulip_bots/bots/chess/test_chess.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 class TestChessBot(StubBotTestCase):
diff --git a/zulip_bots/zulip_bots/bots/converter/test_converter.py b/zulip_bots/zulip_bots/bots/converter/test_converter.py
index 65741afa..afdbc158 100755
--- a/zulip_bots/zulip_bots/bots/converter/test_converter.py
+++ b/zulip_bots/zulip_bots/bots/converter/test_converter.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 class TestConverterBot(StubBotTestCase):
diff --git a/zulip_bots/zulip_bots/bots/define/test_define.py b/zulip_bots/zulip_bots/bots/define/test_define.py
index 3822fd07..5b088269 100755
--- a/zulip_bots/zulip_bots/bots/define/test_define.py
+++ b/zulip_bots/zulip_bots/bots/define/test_define.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 from unittest.mock import patch
 
diff --git a/zulip_bots/zulip_bots/bots/dialogflow/test_dialogflow.py b/zulip_bots/zulip_bots/bots/dialogflow/test_dialogflow.py
index f7ddc4b4..41970e1a 100644
--- a/zulip_bots/zulip_bots/bots/dialogflow/test_dialogflow.py
+++ b/zulip_bots/zulip_bots/bots/dialogflow/test_dialogflow.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase, read_bot_fixture_data
 
 from contextlib import contextmanager
diff --git a/zulip_bots/zulip_bots/bots/encrypt/test_encrypt.py b/zulip_bots/zulip_bots/bots/encrypt/test_encrypt.py
index adb6807e..7453dcf0 100755
--- a/zulip_bots/zulip_bots/bots/encrypt/test_encrypt.py
+++ b/zulip_bots/zulip_bots/bots/encrypt/test_encrypt.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 class TestEncryptBot(StubBotTestCase):
diff --git a/zulip_bots/zulip_bots/bots/followup/test_followup.py b/zulip_bots/zulip_bots/bots/followup/test_followup.py
index 20196054..564d8726 100755
--- a/zulip_bots/zulip_bots/bots/followup/test_followup.py
+++ b/zulip_bots/zulip_bots/bots/followup/test_followup.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from __future__ import absolute_import
 from __future__ import print_function
 
diff --git a/zulip_bots/zulip_bots/bots/giphy/test_giphy.py b/zulip_bots/zulip_bots/bots/giphy/test_giphy.py
index cc54c762..2abc20ac 100755
--- a/zulip_bots/zulip_bots/bots/giphy/test_giphy.py
+++ b/zulip_bots/zulip_bots/bots/giphy/test_giphy.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from unittest.mock import patch
 from requests.exceptions import HTTPError, ConnectionError
 
diff --git a/zulip_bots/zulip_bots/bots/github_detail/test_github_detail.py b/zulip_bots/zulip_bots/bots/github_detail/test_github_detail.py
index 5adfbb97..cf56ad43 100755
--- a/zulip_bots/zulip_bots/bots/github_detail/test_github_detail.py
+++ b/zulip_bots/zulip_bots/bots/github_detail/test_github_detail.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import (
     StubBotHandler,
     StubBotTestCase,
diff --git a/zulip_bots/zulip_bots/bots/google_search/test_google_search.py b/zulip_bots/zulip_bots/bots/google_search/test_google_search.py
index da3caecd..eb531fc4 100644
--- a/zulip_bots/zulip_bots/bots/google_search/test_google_search.py
+++ b/zulip_bots/zulip_bots/bots/google_search/test_google_search.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 from unittest.mock import patch
diff --git a/zulip_bots/zulip_bots/bots/helloworld/test_helloworld.py b/zulip_bots/zulip_bots/bots/helloworld/test_helloworld.py
index 8396dc96..78a563f3 100755
--- a/zulip_bots/zulip_bots/bots/helloworld/test_helloworld.py
+++ b/zulip_bots/zulip_bots/bots/helloworld/test_helloworld.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 class TestHelpBot(StubBotTestCase):
diff --git a/zulip_bots/zulip_bots/bots/help/test_help.py b/zulip_bots/zulip_bots/bots/help/test_help.py
index 32d2fc70..be2adabf 100755
--- a/zulip_bots/zulip_bots/bots/help/test_help.py
+++ b/zulip_bots/zulip_bots/bots/help/test_help.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 
 from typing import Any
diff --git a/zulip_bots/zulip_bots/bots/incrementor/test_incrementor.py b/zulip_bots/zulip_bots/bots/incrementor/test_incrementor.py
index 6d344803..a8186fd0 100644
--- a/zulip_bots/zulip_bots/bots/incrementor/test_incrementor.py
+++ b/zulip_bots/zulip_bots/bots/incrementor/test_incrementor.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 import mock
 
 from zulip_bots.test_lib import (
diff --git a/zulip_bots/zulip_bots/bots/tictactoe/test_tictactoe.py b/zulip_bots/zulip_bots/bots/tictactoe/test_tictactoe.py
index b98f270c..aba3765f 100644
--- a/zulip_bots/zulip_bots/bots/tictactoe/test_tictactoe.py
+++ b/zulip_bots/zulip_bots/bots/tictactoe/test_tictactoe.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python
 from zulip_bots.test_lib import StubBotTestCase
 
 class TestTictactoeBot(StubBotTestCase):
diff --git a/zulip_bots/zulip_bots/bots/wikipedia/test_wikipedia.py b/zulip_bots/zulip_bots/bots/wikipedia/test_wikipedia.py
index 0824125b..e0b2b44b 100755
--- a/zulip_bots/zulip_bots/bots/wikipedia/test_wikipedia.py
+++ b/zulip_bots/zulip_bots/bots/wikipedia/test_wikipedia.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from zulip_bots.test_lib import StubBotTestCase
 from zulip_bots.request_test_lib import mock_request_exception
 
diff --git a/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py b/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
index b83b8a2b..eb3e3f0b 100755
--- a/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
+++ b/zulip_bots/zulip_bots/bots/xkcd/test_xkcd.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 import mock
 from mock import MagicMock, patch
 from zulip_bots.test_lib import StubBotTestCase
diff --git a/zulip_bots/zulip_bots/bots/youtube/test_youtube.py b/zulip_bots/zulip_bots/bots/youtube/test_youtube.py
index 0ddf2327..fea4aaf3 100644
--- a/zulip_bots/zulip_bots/bots/youtube/test_youtube.py
+++ b/zulip_bots/zulip_bots/bots/youtube/test_youtube.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 from __future__ import absolute_import
 
 from unittest.mock import patch
diff --git a/zulip_bots/zulip_bots/provision.py b/zulip_bots/zulip_bots/provision.py
index a9954904..2471e164 100755
--- a/zulip_bots/zulip_bots/provision.py
+++ b/zulip_bots/zulip_bots/provision.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 from __future__ import absolute_import
 
diff --git a/zulip_bots/zulip_bots/run.py b/zulip_bots/zulip_bots/run.py
index a623e114..befb1cd6 100755
--- a/zulip_bots/zulip_bots/run.py
+++ b/zulip_bots/zulip_bots/run.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 from __future__ import print_function
 from __future__ import absolute_import
 
diff --git a/zulip_bots/zulip_bots/terminal.py b/zulip_bots/zulip_bots/terminal.py
index 50430974..2759bf1d 100644
--- a/zulip_bots/zulip_bots/terminal.py
+++ b/zulip_bots/zulip_bots/terminal.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 import os
 import sys
 import argparse
diff --git a/zulip_bots/zulip_bots/test_run.py b/zulip_bots/zulip_bots/test_run.py
index 7c902011..55b0f4ed 100644
--- a/zulip_bots/zulip_bots/test_run.py
+++ b/zulip_bots/zulip_bots/test_run.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 from __future__ import absolute_import
 
 import importlib