Improve error message when a plugin fails to import

CHANGELOG.rst

@@ -5,6 +5,11 @@
 
 *
 
+*
+
+* Improve error message when a plugin fails to load.
+  Thanks `@nicoddemus`_ for the PR.
+
 * Fix (`#1178 <https://github.com/pytest-dev/pytest/issues/1178>`_):
   ``pytest.fail`` with non-ascii characters raises an internal pytest error.
   Thanks `@nicoddemus`_ for the PR.
@@ -12,7 +17,6 @@
 * Fix (`#469`_): junit parses report.nodeid incorrectly, when params IDs
   contain ``::``. Thanks `@tomviner`_ for the PR (`#1431`_).
 
-
 * Fix (`#578 <https://github.com/pytest-dev/pytest/issues/578>`_): SyntaxErrors
   containing non-ascii lines at the point of failure generated an internal
   py.test error.
@@ -23,6 +27,8 @@
 
 *
 
+*
+
 
 .. _#1437: https://github.com/pytest-dev/pytest/issues/1437
 .. _#469: https://github.com/pytest-dev/pytest/issues/469

_pytest/config.py

@@ -383,8 +383,8 @@ class PytestPluginManager(PluginManager):
             importspec = modname
         try:
             __import__(importspec)
-        except ImportError:
-            raise
+        except ImportError as e:
+            raise ImportError('Error importing plugin "%s": %s' % (modname, e))
         except Exception as e:
             import pytest
             if not hasattr(pytest, 'skip') or not isinstance(e, pytest.skip.Exception):

testing/test_pluginmanager.py

@@ -178,13 +178,17 @@ def test_default_markers(testdir):
         "*trylast*last*",
     ])
 
+
 def test_importplugin_issue375(testdir, pytestpm):
+    """Don't hide import errors when importing plugins and provide
+    an easy to debug message.
+    """
     testdir.syspathinsert(testdir.tmpdir)
     testdir.makepyfile(qwe="import aaaa")
     with pytest.raises(ImportError) as excinfo:
         pytestpm.import_plugin("qwe")
-    assert "qwe" not in str(excinfo.value)
-    assert "aaaa" in str(excinfo.value)
+    expected = '.*Error importing plugin "qwe": No module named \'?aaaa\'?'
+    assert py.std.re.match(expected, str(excinfo.value))
 
 
 class TestPytestPluginManager: