Merge pull request #607 from kaczmarj/kaczmarj-bf

MRG: preserve error output if not valid klass in `nibabel.save()`

This PR adds a fix for an `UnboundLocalError` in `nibabel.save`

Author: matthew-brett

nibabel/loadsave.py

@@ -133,10 +133,10 @@ def save(img, filename):
                 converted = klass.from_image(img)
                 break
             except Exception as e:
-                continue
+                err = e
         # ... and if none of them work, raise an error.
         if converted is None:
-            raise e
+            raise err
 
     # Here, we either have a klass or a converted image.
     if converted is None:

nibabel/tests/test_image_load_save.py

@@ -30,7 +30,7 @@
 from ..spatialimages import SpatialImage
 
 from numpy.testing import assert_array_equal, assert_array_almost_equal
-from nose.tools import assert_true, assert_equal
+from nose.tools import assert_true, assert_equal, assert_raises
 
 _, have_scipy, _ = optional_package('scipy')  # No scipy=>no SPM-format writing
 DATA_PATH = pjoin(dirname(__file__), 'data')
@@ -322,3 +322,14 @@ def test_guessed_image_type():
     assert_equal(nils.guessed_image_type(
         pjoin(DATA_PATH, 'analyze.hdr')),
         Spm2AnalyzeImage)
+
+
+def test_fail_save():
+    with InTemporaryDirectory():
+        dataobj = np.ones((10, 10, 10), dtype=np.float16)
+        affine = np.eye(4, dtype=np.float32)
+        img = SpatialImage(dataobj, affine)
+        # Fails because float16 is not supported.
+        with assert_raises(AttributeError):
+            nils.save(img, 'foo.nii.gz')
+        del img