Add Python 2 check to `wagtail` command

CHANGELOG.txt

@@ -34,6 +34,7 @@ Changelog
 2.0.1 (xx.xx.xxxx) - IN DEVELOPMENT
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+ * Added error notification when running the `wagtail` command on Python <3.4 (Matt Westcott)
  * Fix: Draftail now supports features specified via the `WAGTAILADMIN_RICH_TEXT_EDITORS` setting (Todd Dembrey)
  * Fix: Password reset form no longer indicates whether the email is recognised, as per standard Django behaviour (Bertrand Bordage)
  * Fix: `UserAttributeSimilarityValidator` is now correctly enforced on user creation / editing forms (Tim Heap)

docs/releases/2.0.1.rst

@@ -10,6 +10,8 @@ Wagtail 2.0.1 release notes - IN DEVELOPMENT
 What's new
 ==========
 
+ * Added error notification when running the ``wagtail`` command on Python <3.4 (Matt Westcott)
+
 Bug fixes
 ~~~~~~~~~
 

wagtail/bin/wagtail.py

@@ -8,6 +8,16 @@ from argparse import ArgumentParser
 from difflib import unified_diff
 
 from django.core.management import ManagementUtility
+# Need to use the django.utils.six version of print, to avoid a syntax error on Py2 when using print(..., end='')
+from django.utils.six import print_
+
+
+CURRENT_PYTHON = sys.version_info[:2]
+REQUIRED_PYTHON = (3, 4)
+
+if CURRENT_PYTHON < REQUIRED_PYTHON:
+    sys.stderr.write("This version of Wagtail requires Python {}.{} or above - you are running {}.{}\n".format(*(REQUIRED_PYTHON + CURRENT_PYTHON)))
+    sys.exit(1)
 
 
 def pluralize(value, arg='s'):
@@ -227,7 +237,7 @@ class UpdateModulePaths(Command):
         with fileinput.FileInput(filename, inplace=True) as f:
             for original_line in f:
                 line = self._rewrite_line(original_line)
-                print(line, end='')  # NOQA
+                print_(line, end='')  # NOQA
                 if line != original_line:
                     change_count += 1