4 files changed, 23 insertions, 6 deletions
diff --git a/dimension/tests/demo.dmnsn b/dimension/tests/demo.dmnsn
index 040ae4f..3a04abc 100644
--- a/dimension/tests/demo.dmnsn
+++ b/dimension/tests/demo.dmnsn
@@ -23,10 +23,16 @@ camera = PerspectiveCamera(location = (0, 0.25, -4),
 camera.rotate(53*Y)
 
 # Background
+
+try:
+  image_map = ImageMap("../../libdimension/tests/png2.png").rotate(53*Y)
+except OSError:
+  image_map = Orange
+
 background = PigmentMap(
   pattern = Gradient(Y),
   map     = {
-    0:    ImageMap("../../libdimension/tests/png2.png").rotate(53*Y),
+    0:    image_map,
     0.35: Color(0, 0.1, 0.2, trans = 0.1, filter = 0.0),
   },
 )
diff --git a/libdimension-python/dimension.pyx b/libdimension-python/dimension.pyx
index b8855fe..dffa8fa 100644
--- a/libdimension-python/dimension.pyx
+++ b/libdimension-python/dimension.pyx
@@ -569,9 +569,19 @@ cdef class Canvas:
       if fclose(file) != 0:
         _raise_OSError()
 
-    progress = _Progress(dmnsn_png_write_canvas_async(self._canvas, file))
-    progress._finalizer = finalize
-    return progress
+    cdef dmnsn_progress *progress = dmnsn_png_write_canvas_async(self._canvas,
+                                                                 file)
+
+    try:
+      if progress == NULL:
+        _raise_OSError()
+
+      ret = _Progress(progress)
+      ret._finalizer = finalize
+      return ret
+    except:
+      finalize()
+      raise
 
   def draw_GL(self):
     """Export the canvas to the current OpenGL context."""
diff --git a/libdimension-python/tests/canvas.py b/libdimension-python/tests/canvas.py
index 3b2057e..239a548 100755
--- a/libdimension-python/tests/canvas.py
+++ b/libdimension-python/tests/canvas.py
@@ -19,8 +19,8 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>. #
 #########################################################################
 
-from dimension import *
 import errno
+from dimension import *
 
 # Treat warnings as errors for tests
 die_on_warnings(True)
@@ -35,7 +35,7 @@ try:
     canvas.optimize_PNG()
 except OSError as e:
     if e.errno == errno.ENOSYS:
-        havePNG = False
+        have_PNG = False
     else:
         raise
 
diff --git a/libdimension-python/tests/demo.py b/libdimension-python/tests/demo.py
index fe3518c..a9774bc 100755
--- a/libdimension-python/tests/demo.py
+++ b/libdimension-python/tests/demo.py
@@ -21,6 +21,7 @@
 
 import os
 import os.path
+import errno
 from math import *
 from dimension import *