[pygobject] Raise ImportError when importing modules not found in repository

[Simon Feltman <sfeltman src gnome org>]

commit ac8b59ee335967efef974ab0aa89128ade9f3d0c
Author: Simon Feltman <sfeltman src gnome org>
Date:   Mon Mar 24 18:09:10 2014 -0700

    Raise ImportError when importing modules not found in repository
    
    Raise an ImportError with extra information noting the typelib was not
    found. This removes the need to log a similar message which adds output
    noise when attempting controlled imports within try/except statements.
    In Python 2, the additional information is lost but in Python 3 it shows up.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=726877

 gi/importer.py                 |    9 ++++-----
 tests/test_import_machinery.py |   18 ++++++++++++++++++
 2 files changed, 22 insertions(+), 5 deletions(-)
---
diff --git a/gi/importer.py b/gi/importer.py
index aa95cf6..cea0f8b 100644
--- a/gi/importer.py
+++ b/gi/importer.py
@@ -21,7 +21,6 @@
 # USA
 
 from __future__ import absolute_import
-import logging
 import sys
 
 from ._gi import Repository
@@ -47,11 +46,11 @@ class DynamicImporter(object):
         if path != self.path:
             return
 
-        if not repository.enumerate_versions(namespace):
-            logging.error('Could not find any typelib for %s', namespace)
-            return None
-        else:
+        if repository.enumerate_versions(namespace):
             return self
+        else:
+            raise ImportError('cannot import name %s, '
+                              'introspection typelib not found' % namespace)
 
     def load_module(self, fullname):
         if fullname in sys.modules:
diff --git a/tests/test_import_machinery.py b/tests/test_import_machinery.py
index e1af1f1..42b4bf8 100644
--- a/tests/test_import_machinery.py
+++ b/tests/test_import_machinery.py
@@ -1,6 +1,7 @@
 # -*- Mode: Python; py-indent-offset: 4 -*-
 # vim: tabstop=4 shiftwidth=4 expandtab
 
+import sys
 import unittest
 
 import gi.overrides
@@ -56,3 +57,20 @@ class TestModule(unittest.TestCase):
 
         # Restore the previous cache
         gi.module._introspection_modules = old_modules
+
+
+class TestImporter(unittest.TestCase):
+    def test_invalid_repository_module_name(self):
+        with self.assertRaises(ImportError) as context:
+            from gi.repository import InvalidGObjectRepositoryModuleName
+            InvalidGObjectRepositoryModuleName  # pyflakes
+
+        exception_string = str(context.exception)
+
+        self.assertTrue('InvalidGObjectRepositoryModuleName' in exception_string)
+
+        # The message of the custom exception in gi/importer.py is eaten in Python 2.7
+        if sys.version_info.major < 3:
+            self.assertTrue('introspection typelib' not in exception_string)
+        else:
+            self.assertTrue('introspection typelib' in exception_string)