BF: Fix issue where unicode paths were not recognized as files.

Fixes issue where output files with unicode paths were always
being deleted if remove_unnecessary_outputs was set to True.

Author: moloney

nipype/pipeline/utils.py

@@ -634,7 +634,7 @@ def walk_outputs(object):
             if isdefined(val):
                 out.extend(walk_outputs(val))
     else:
-        if isdefined(object) and isinstance(object, str):
+        if isdefined(object) and isinstance(object, basestring):
             if os.path.islink(object) or os.path.isfile(object):
                 out = [(filename, 'f') for filename in get_all_files(object)]
             elif os.path.isdir(object):