--- a/cubicweb/__init__.py	Wed Jul 06 17:46:39 2016 +0200
+++ b/cubicweb/__init__.py	Wed Aug 31 11:53:21 2016 +0200
@@ -20,6 +20,7 @@
 """
 __docformat__ = "restructuredtext en"
 
+import imp
 import logging
 import os
 import pickle
@@ -280,3 +281,41 @@
     not be processed, a memory allocation error occurred during processing,
     etc.
     """
+
+
+# Import hook for "legacy" cubes ##############################################
+
+class _CubesImporter(object):
+    """Module finder handling redirection of import of "cubes.<name>"
+    to "cubicweb_<name>".
+    """
+
+    @classmethod
+    def install(cls):
+        if not any(isinstance(x, cls) for x in sys.meta_path):
+            self = cls()
+            sys.meta_path.append(self)
+
+    def find_module(self, fullname, path=None):
+        if fullname.startswith('cubes.'):
+            modname = 'cubicweb_' + fullname.split('.', 1)[1]
+            try:
+                modinfo = imp.find_module(modname)
+            except ImportError:
+                return None
+            else:
+                return _CubesLoader(modinfo)
+
+
+class _CubesLoader(object):
+    """Module loader handling redirection of import of "cubes.<name>"
+    to "cubicweb_<name>".
+    """
+
+    def __init__(self, modinfo):
+        self.modinfo = modinfo
+
+    def load_module(self, fullname):
+        if fullname not in sys.modules:  # Otherwise, it's a reload.
+            sys.modules[fullname] = imp.load_module(fullname, *self.modinfo)
+        return sys.modules[fullname]

--- a/cubicweb/cwconfig.py	Wed Jul 06 17:46:39 2016 +0200
+++ b/cubicweb/cwconfig.py	Wed Aug 31 11:53:21 2016 +0200
@@ -605,6 +605,8 @@
     @classmethod
     def cls_adjust_sys_path(cls):
         """update python path if necessary"""
+        from cubicweb import _CubesImporter
+        _CubesImporter.install()
         cubes_parent_dir = normpath(join(cls.CUBES_DIR, '..'))
         if not cubes_parent_dir in sys.path:
             sys.path.insert(0, cubes_parent_dir)

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cubicweb/test/unittest_cubes.py	Wed Aug 31 11:53:21 2016 +0200
@@ -0,0 +1,123 @@
+# copyright 2016 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
+# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
+#
+# This file is part of CubicWeb.
+#
+# CubicWeb is free software: you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation, either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# CubicWeb is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with CubicWeb.  If not, see <http://www.gnu.org/licenses/>.
+"""Unit tests for "cubes" importer."""
+
+from contextlib import contextmanager
+import os
+from os import path
+import shutil
+import sys
+import tempfile
+import unittest
+
+from six import PY2
+
+from cubicweb import _CubesImporter
+from cubicweb.cwconfig import CubicWebConfiguration
+
+
+@contextmanager
+def temp_cube():
+    tempdir = tempfile.mkdtemp()
+    try:
+        libdir = path.join(tempdir, 'libpython')
+        cubedir = path.join(libdir, 'cubicweb_foo')
+        os.makedirs(cubedir)
+        with open(path.join(cubedir, '__init__.py'), 'w') as f:
+            f.write('"""cubicweb_foo application package"""')
+        with open(path.join(cubedir, 'bar.py'), 'w') as f:
+            f.write('baz = 1')
+        sys.path.append(libdir)
+        yield cubedir
+    finally:
+        shutil.rmtree(tempdir)
+        sys.path.remove(libdir)
+
+
+class CubesImporterTC(unittest.TestCase):
+
+    def setUp(self):
+        # During discovery, CubicWebConfiguration.cls_adjust_sys_path may be
+        # called (probably because of cubicweb.devtools's __init__.py), so
+        # uninstall _CubesImporter.
+        for x in sys.meta_path:
+            if isinstance(x, _CubesImporter):
+                sys.meta_path.remove(x)
+        # Keep track of initial sys.path and sys.meta_path.
+        self.orig_sys_path = sys.path[:]
+        self.orig_sys_meta_path = sys.meta_path[:]
+
+    def tearDown(self):
+        # Cleanup any imported "cubes".
+        for name in list(sys.modules):
+            if name.startswith('cubes') or name.startswith('cubicweb_'):
+                del sys.modules[name]
+        # Restore sys.{meta_,}path
+        sys.path[:] = self.orig_sys_path
+        sys.meta_path[:] = self.orig_sys_meta_path
+
+    def test_importer_install(self):
+        _CubesImporter.install()
+        self.assertIsInstance(sys.meta_path[-1], _CubesImporter)
+
+    def test_config_installs_importer(self):
+        CubicWebConfiguration.cls_adjust_sys_path()
+        self.assertIsInstance(sys.meta_path[-1], _CubesImporter)
+
+    def test_import_cube_as_package_legacy_name(self):
+        """Check for import of an actual package-cube using legacy name"""
+        with temp_cube() as cubedir:
+            import cubicweb_foo  # noqa
+            del sys.modules['cubicweb_foo']
+            with self.assertRaises(ImportError):
+                import cubes.foo
+            CubicWebConfiguration.cls_adjust_sys_path()
+            import cubes.foo  # noqa
+            self.assertEqual(cubes.foo.__path__, [cubedir])
+            self.assertEqual(cubes.foo.__doc__,
+                             'cubicweb_foo application package')
+            # Import a submodule.
+            from cubes.foo import bar
+            self.assertEqual(bar.baz, 1)
+
+    def test_import_legacy_cube(self):
+        """Check that importing a legacy cube works when sys.path got adjusted.
+        """
+        CubicWebConfiguration.cls_adjust_sys_path()
+        import cubes.card  # noqa
+
+    def test_import_cube_as_package_after_legacy_cube(self):
+        """Check import of a "cube as package" after a legacy cube."""
+        CubicWebConfiguration.cls_adjust_sys_path()
+        with temp_cube() as cubedir:
+            import cubes.card
+            import cubes.foo
+        self.assertEqual(cubes.foo.__path__, [cubedir])
+
+    def test_cube_inexistant(self):
+        """Check for import of an inexistant cube"""
+        CubicWebConfiguration.cls_adjust_sys_path()
+        with self.assertRaises(ImportError) as cm:
+            import cubes.doesnotexists  # noqa
+        msg = "No module named " + ("doesnotexists" if PY2 else "'cubes.doesnotexists'")
+        self.assertEqual(str(cm.exception), msg)
+
+
+if __name__ == '__main__':
+    import unittest
+    unittest.main()