get_willow_image now raises SourceImageIOError

... when the source image cannot be found in the filesystem

wagtail/wagtailimages/models.py

@@ -82,7 +82,13 @@ class AbstractImage(models.Model, TagSearchable):
         return self.title
 
     def get_willow_image(self):
-        image_file = self.file.file
+        try:
+            image_file = self.file.file  # triggers a call to self.storage.open, so IOErrors from missing files will be raised at this point
+        except IOError as e:
+            # re-throw this as a SourceImageIOError so that calling code can distinguish
+            # these from IOErrors elsewhere in the process
+            raise SourceImageIOError(text_type(e))
+
         image_file.open('rb')
         image_file.seek(0)
 

wagtail/wagtailimages/tests/test_models.py

@@ -14,7 +14,7 @@ from django.db import connection
 from wagtail.tests.utils import WagtailTestUtils, test_concurrently
 from wagtail.wagtailcore.models import Page
 from wagtail.tests.models import EventPage, EventPageCarouselItem
-from wagtail.wagtailimages.models import Rendition, Filter
+from wagtail.wagtailimages.models import Rendition, Filter, SourceImageIOError
 from wagtail.wagtailimages.backends import get_image_backend
 from wagtail.wagtailimages.backends.pillow import PillowBackend
 from wagtail.wagtailimages.rect import Rect
@@ -269,7 +269,9 @@ class TestGetUsage(TestCase):
         self.assertTrue(issubclass(Page, type(self.image.get_usage()[0])))
 
 
-def TestGetWillowImage(TestCase):
+class TestGetWillowImage(TestCase):
+    fixtures = ['test.json']
+
     def setUp(self):
         self.image = Image.objects.create(
             title="Test image",
@@ -281,6 +283,14 @@ def TestGetWillowImage(TestCase):
 
         self.assertIsInstance(willow_image, WillowImage)
 
+    def test_with_missing_image(self):
+        # Image id=1 in test fixtures has a missing image file
+        bad_image = Image.objects.get(id=1)
+
+        # Attempting to get the Willow image for images without files
+        # should raise a SourceImageIOError
+        self.assertRaises(SourceImageIOError, bad_image.get_willow_image)
+
 
 class TestIssue573(TestCase):
     """