Check for and warn about missing assets in setup.py install

setup.py

@@ -1,13 +1,11 @@
 #!/usr/bin/env python
 
 import sys
-import os
 
 from setuptools.command.sdist import sdist
 
 from wagtail.wagtailcore import __version__
-from wagtail.utils.setup import assets, add_subcommand
-
+from wagtail.utils.setup import assets, add_subcommand, check_bdist_egg
 
 try:
     from setuptools import setup, find_packages
@@ -83,6 +81,7 @@ setup(
     zip_safe=False,
     cmdclass={
         'sdist': add_subcommand(sdist, [('assets', None)]),
+        'bdist_egg': check_bdist_egg,
         'assets': assets,
     },
 )

wagtail/utils/setup.py

@@ -1,8 +1,12 @@
 from __future__ import absolute_import, print_function, unicode_literals
+
+import os
 import subprocess
 
 from distutils.core import Command
 
+from setuptools.command.bdist_egg import bdist_egg
+
 
 class assets(Command):
 
@@ -22,10 +26,26 @@ class assets(Command):
             raise SystemExit(1)
 
 
+class check_bdist_egg(bdist_egg):
+
+    # If this file does not exist, warn the user to compile the assets
+    sentinel_file = 'wagtail/wagtailadmin/static/wagtailadmin/css/core.css'
+
+    def run(self):
+        bdist_egg.run(self)
+        if not os.path.isfile(self.sentinel_file):
+            print("\n".join([
+                "************************************************************",
+                "The front end assets for Wagtail are missing.",
+                "To generate the assets, please refer to the documentation in",
+                "docs/contributing/css_guidelines.rst",
+                "************************************************************",
+            ]))
+
+
 def add_subcommand(command, extra_sub_commands):
     # Sadly, as commands are old-style classes, `type()` can not be used to
-    # construct these. Additionally, old-style classes do not have a `name`
-    # attribute, so naming them nicely is also impossible.
+    # construct these.
     class CompileAnd(command):
         sub_commands = command.sub_commands + extra_sub_commands
     CompileAnd.__name__ = command.__name__