RF: Add testing for file existence up front.

Raises an informative error when the file doesn't exist.

Author: arokem

nibabel/loadsave.py

@@ -9,6 +9,7 @@
 # module imports
 """ Utilities to load and save image objects """
 
+import os.path as op
 import numpy as np
 import warnings
 
@@ -34,6 +35,8 @@ def load(filename, **kwargs):
     img : ``SpatialImage``
        Image of guessed type
     '''
+    if not op.exists(filename):
+        raise FileNotFoundError("No such file: '%s'" % filename)
     sniff = None
     for image_klass in all_image_classes:
         is_valid, sniff = image_klass.path_maybe_image(filename, sniff)