Error if submodules are not initialized yet

.gitignore

@@ -54,6 +54,7 @@ sassc/
 sass-spec/
 
 # libsass-python
+._.DS_Store
 build/
 dist/
 docs/_build

setup.py

@@ -1,4 +1,4 @@
-from __future__ import with_statement
+from __future__ import print_function, with_statement
 
 import ast
 import distutils.cmd
@@ -44,6 +44,13 @@
 sources = ['pysass.c']
 sources.extend(libsass_sources)
 
+if not os.path.isdir('sass2scss') and os.path.isdir('.git'):
+    print('Submodules seem not initialized yet.'
+          'You can initialize it by the following command:',
+          file=sys.stderr)
+    print('\tgit submodule update --init', file=sys.stderr)
+    raise SystemExit(1)
+
 if sys.platform == 'win32':
     from distutils.msvc9compiler import get_build_version
     vscomntools_env = 'VS{0}{1}COMNTOOLS'.format(