Description: Fix Python shebang for various scripts

Pagure ships with the "/usr/bin/env python" shebang, which doesn't
work on Debian because "python" refers to Python 2.  This patch
replaces every occurrence of this by "/usr/bin/python3".

Author: Sergio Durigan Junior <sergiodj@sergiodj.net>
Forwarded: sort of, https://pagure.io/pagure/issue/4725

--- a/createdb.py
+++ b/createdb.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 from __future__ import print_function, unicode_literals, absolute_import
 
--- a/files/aclchecker.py
+++ b/files/aclchecker.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/files/api_key_expire_mail.py
+++ b/files/api_key_expire_mail.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 from __future__ import print_function, absolute_import
 import os
--- a/files/emoji_clean_json.py
+++ b/files/emoji_clean_json.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 from __future__ import print_function, absolute_import
 import json
--- a/files/keyhelper.py
+++ b/files/keyhelper.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/files/mirror_project_in.py
+++ b/files/mirror_project_in.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 from __future__ import print_function, absolute_import
 import os
--- a/files/pagure_mirror_project_in.service
+++ b/files/pagure_mirror_project_in.service
@@ -9,7 +9,7 @@ Description=Pagure service to mirror in
 Documentation=https://pagure.io/pagure
 
 [Service]
-ExecStart=/usr/bin/python /usr/share/pagure/mirror_project_in.py
+ExecStart=/usr/bin/python3 /usr/share/pagure/mirror_project_in.py
 Environment="PAGURE_CONFIG=/etc/pagure/pagure.cfg"
 Type=simple
 User=git
--- a/pagure-ev/pagure_stream_server.py
+++ b/pagure-ev/pagure_stream_server.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 """
  (c) 2015-2017 - Copyright Red Hat Inc
--- a/pagure-milters/comment_email_milter.py
+++ b/pagure-milters/comment_email_milter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 # Milter calls methods of your class at milter events.
--- a/pagure/hooks/files/git_multimail_upstream.py
+++ b/pagure/hooks/files/git_multimail_upstream.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 __version__ = "1.4.0"
 
--- a/pagure/hooks/files/hookrunner
+++ b/pagure/hooks/files/hookrunner
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/pagure/hooks/files/repospannerhook
+++ b/pagure/hooks/files/repospannerhook
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 """
 Setup script
--- a/tests/test_fnmatch.py
+++ b/tests/test_fnmatch.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/tests/test_pagure_flask_ui_issues_acl_checks.py
+++ b/tests/test_pagure_flask_ui_issues_acl_checks.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # coding=utf-8
 
 """
--- a/tests/test_stream_server.py
+++ b/tests/test_stream_server.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """
--- a/tests/test_style.py
+++ b/tests/test_style.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 # -*- coding: utf-8 -*-
 
 """