just pretend attributes of unimportable lazy modules don't exist

Suggested by Diana Clarke.

3 files changed, 21 insertions, 14 deletions

diff --git a/CHANGES b/CHANGES
index f9d3530..3dae7cb 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,8 @@ This file lists the changes in each six version.
 Development version
 -------------------
 
+- Raise an AttributeError for every attribute of unimportable modules.
+
 - Issue #56: Make the fake modules six.moves puts into sys.modules appear not to
   have a __path__ unless they are loaded.
 
diff --git a/documentation/index.rst b/documentation/index.rst
index 99e82e1..3d7828b 100644
--- a/documentation/index.rst
+++ b/documentation/index.rst
@@ -450,11 +450,11 @@ functionality; its structure mimics the structure of the Python 3
    interpreter. For example, ``sys.modules["six.moves.winreg"].LoadKey`` would
    fail on any non-Windows platform. Unfortunately, some applications try to
    load attributes on every module in :data:`py3:sys.modules`. six mitigates
-   this problem for some applications by pretending ``__file__`` and
-   ``__name__`` don't exist on lazy modules that aren't loaded. That doesn't
-   work in every case, though. If you are encountering this problem and don't
-   use any from imports directly from ``six.moves`` modules, you can workaround
-   the issue by removing the six proxy modules::
+   this problem for some applications by pretending attributes on unimportable
+   modules don't exist. This hack doesn't work in every case, though. If you are
+   encountering problems with the lazy modules and don't use any from imports
+   directly from ``six.moves`` modules, you can workaround the issue by removing
+   the six proxy modules::
 
      d = [name for name in sys.modules if name.startswith("six.moves.")]
      for name in d:
diff --git a/six.py b/six.py
index 58cb95b..c86dc98 100644
--- a/six.py
+++ b/six.py
@@ -105,17 +105,22 @@ class MovedModule(_LazyDescr):
         return _import_module(self.mod)
 
     def __getattr__(self, attr):
-        # Hack around the Django autoreloader. The reloader tries to get
-        # __file__ or __name__ of every module in sys.modules. This doesn't work
-        # well if this MovedModule is for an module that is unavailable on this
-        # machine (like winreg on Unix systems). Thus, we pretend __file__ and
-        # __name__ don't exist if the module hasn't been loaded yet. We give
-        # __path__ the same treatment for Google AppEngine. See issues #51, #53
-        # and #56.
+        # It turns out many Python frameworks like to traverse sys.modules and
+        # try to load various attributes. This causes problems if this is a
+        # platform-specific module on the wrong platform, like _winreg on
+        # Unixes. Therefore, we silently pretend unimportable modules do not
+        # have any attributes. See issues #51, #53, #56, and #63 for the full
+        # tales of woe.
+        #
+        # First, if possible, avoid loading the module just to look at __file__,
+        # __name__, or __path__.
         if (attr in ("__file__", "__name__", "__path__") and
             self.mod not in sys.modules):
-            raise AttributeError
-        _module = self._resolve()
+            raise AttributeError(attr)
+        try:
+            _module = self._resolve()
+        except ImportError:
+            raise AttributeError(attr)
         value = getattr(_module, attr)
         setattr(self, attr, value)
         return value