bugfix for issue #2491

_pytest/config.py

@@ -5,6 +5,7 @@
 import traceback
 import types
 import warnings
+import six
 
 import py
 # DON't import pytest here because it causes import cycle troubles
@@ -442,12 +443,12 @@ def import_plugin(self, modname):
         try:
             __import__(importspec)
         except ImportError as e:
-            new_exc = ImportError('Error importing plugin "%s": %s' % (modname, safe_str(e.args[0])))
-            # copy over name and path attributes
-            for attr in ('name', 'path'):
-                if hasattr(e, attr):
-                    setattr(new_exc, attr, getattr(e, attr))
-            raise new_exc
+            new_exc_type = ImportError
+            new_exc_message = 'Error importing plugin "%s": %s' % (modname, safe_str(e.args[0]))
+            new_exc = new_exc_type(new_exc_message)
+
+            six.reraise(new_exc_type, new_exc, sys.exc_info()[2])
+
         except Exception as e:
             import pytest
             if not hasattr(pytest, 'skip') or not isinstance(e, pytest.skip.Exception):

changelog/2491.bugfix

@@ -0,0 +1,4 @@
+If an exception happens while loading a plugin, PyTest no longer hides the original traceback.
+In python2 it will show the original traceback with a new message that explains in which plugin.
+In python3 it will show 2 canonized exceptions, the original exception while loading the plugin
+in addition to an exception that PyTest throws about loading a plugin.

setup.py

@@ -43,7 +43,7 @@ def has_environment_marker_support():
 
 
 def main():
-    install_requires = ['py>=1.4.33', 'setuptools']  # pluggy is vendored in _pytest.vendored_packages
+    install_requires = ['py>=1.4.33', 'setuptools', 'six']  # pluggy is vendored in _pytest.vendored_packages
     extras_require = {}
     if has_environment_marker_support():
         extras_require[':python_version=="2.6"'] = ['argparse', 'ordereddict']

testing/test_pluginmanager.py

@@ -216,12 +216,17 @@ def test_importplugin_error_message(testdir, pytestpm):
     testdir.syspathinsert(testdir.tmpdir)
     testdir.makepyfile(qwe="""
         # encoding: UTF-8
-        raise ImportError(u'Not possible to import: ☺')
+        def test_traceback():
+            raise ImportError(u'Not possible to import: ☺')
+
+        test_traceback()
     """)
     with pytest.raises(ImportError) as excinfo:
         pytestpm.import_plugin("qwe")
-    expected = '.*Error importing plugin "qwe": Not possible to import: .'
-    assert py.std.re.match(expected, str(excinfo.value))
+    expected_message = '.*Error importing plugin "qwe": Not possible to import: .'
+    expected_traceback = ".*in test_traceback"
+    assert py.std.re.match(expected_message, str(excinfo.value))
+    assert py.std.re.match(expected_traceback, str(excinfo.traceback[-1]))
 
 
 class TestPytestPluginManager(object):