This bookmark adds structured exceptions to astroid.

Major changes:
* AstroidError has an __init__ that accepts arbitrary keyword-only
  arguments for adding information to exceptions, and a __str__ that
  lazily uses exception attributes to generate a message.  The first
  positional argument to an exception is assigned to .message.  The new
  API should be fully backwards compatible in general.
* Some exceptions are combined or renamed; the old names are still
  available.
* The OperationErrors used by pylint are now BadOperationMessages and
  located in util.py.
* The AstroidBuildingException in _data_build stores the SyntaxError
  in its .error attribute rather than args[0].
* Many places where exceptions are raised have new, hopefully more
  useful error messages.

The only major issue remaining is how to propagate information into decorators.

1 files changed, 15 insertions, 5 deletions

diff --git a/astroid/mixins.py b/astroid/mixins.py
index 9f5f9538..6ee7b4db 100644
--- a/astroid/mixins.py
+++ b/astroid/mixins.py
@@ -129,11 +129,19 @@ class ImportFromMixin(FilterStmtsMixin):
             return mymodule.import_module(modname, level=level,
                                           relative_only=level and level >= 1)
         except exceptions.AstroidBuildingException as ex:
-            if isinstance(ex.args[0], SyntaxError):
-                util.reraise(exceptions.InferenceError(str(ex)))
-            util.reraise(exceptions.InferenceError(modname))
+            if isinstance(getattr(ex, 'error', None), SyntaxError):
+                util.reraise(exceptions.InferenceError(
+                    'Could not import {modname} because of SyntaxError:\n'
+                    '{syntax_error}', modname=modname, syntax_error=ex.error,
+                    import_node=self))
+            util.reraise(exceptions.InferenceError('Could not import {modname}.',
+                                                   modname=modname,
+                                                   import_node=self))
         except SyntaxError as ex:
-            util.reraise(exceptions.InferenceError(str(ex)))
+            util.reraise(exceptions.InferenceError(
+                'Could not import {modname} because of SyntaxError:\n'
+                '{syntax_error}', modname=modname, syntax_error=ex,
+                import_node=self))
 
     def real_name(self, asname):
         """get name from 'as' name"""
@@ -145,4 +153,6 @@ class ImportFromMixin(FilterStmtsMixin):
                 _asname = name
             if asname == _asname:
                 return name
-        raise exceptions.NotFoundError(asname)
+        raise exceptions.AttributeInferenceError(
+            'Could not find original name for {attribute} in {target!r}',
+            target=self, attribute=asname)