OWLoadClassifier: Show message about unpickling error

Orange/widgets/classify/owloadclassifier.py

@@ -12,6 +12,7 @@
 from Orange.widgets.utils import stdpaths
 
 from Orange.widgets.classify import owsaveclassifier
+from Orange.widgets.widget import Msg
 
 
 class OWLoadClassifier(widget.OWWidget):
@@ -27,6 +28,9 @@ class OWLoadClassifier(widget.OWWidget):
     #: Current (last selected) filename or None.
     filename = Setting(None)
 
+    class Error(widget.OWWidget.Error):
+        load_error = Msg("An error occured while reading '{}'")
+
     FILTER = owsaveclassifier.OWSaveClassifier.FILTER
 
     want_main_area = False
@@ -96,11 +100,10 @@ def load(self, filename):
         """Load the object from filename and send it to output."""
         try:
             classifier = pickle.load(open(filename, "rb"))
-        except pickle.UnpicklingError:
-            raise  # TODO: error reporting
-        except os.error:
-            raise  # TODO: error reporting
+        except (pickle.UnpicklingError, OSError, EOFError):
+            self.Error.load_error(os.path.split(filename)[-1])
         else:
+            self.Error.load_error.clear()
             self._remember(filename)
             self.send("Classifier", classifier)
 

Orange/widgets/classify/tests/test_owloadclassifier.py

@@ -0,0 +1,32 @@
+# Test methods with long descriptive names can omit docstrings
+# pylint: disable=missing-docstring
+import os
+import pickle
+from tempfile import mkstemp
+
+from Orange.classification.majority import ConstantModel
+from Orange.widgets.classify.owloadclassifier import OWLoadClassifier
+from Orange.widgets.tests.base import WidgetTest
+
+
+class TestOWMajority(WidgetTest):
+    def setUp(self):
+        self.widget = self.create_widget(OWLoadClassifier)
+
+    def test_show_error(self):
+        self.widget.load("no-such-file.pckls")
+        self.assertTrue(self.widget.Error.load_error.is_shown())
+
+        clsf = ConstantModel([1, 1, 1])
+        fd, fname = mkstemp(suffix='.pkcls')
+        try:
+            pickle.dump(clsf, open(fname, "wb"))
+            self.widget.load(fname)
+            self.assertFalse(self.widget.Error.load_error.is_shown())
+
+            open(fname, "w").write("X")
+            self.widget.load(fname)
+            self.assertTrue(self.widget.Error.load_error.is_shown())
+        finally:
+            os.remove(fname)
+