Allow unicode conversion for errors containing non-ascii strings.

fs/errors.py

@@ -39,6 +39,7 @@ __all__ = ['FSError',
 
 import sys
 import errno
+import six
 
 from fs.path import *
 from fs.local_functools import wraps
@@ -63,7 +64,12 @@ class FSError(Exception):
         return str(self.msg % keys)
 
     def __unicode__(self):
-        return unicode(self.msg) % self.__dict__
+        keys = {}
+        for k,v in self.__dict__.iteritems():
+            if isinstance(v, six.binary_type):
+                v = v.decode(sys.getfilesystemencoding(), errors='replace')
+            keys[k] = v
+        return unicode(self.msg, encoding=sys.getfilesystemencoding(), errors='replace') % keys
 
     def __reduce__(self):
         return (self.__class__,(),self.__dict__.copy(),)

fs/tests/test_errors.py

+# -*- encoding: utf-8 -*-
 """
 
   fs.tests.test_errors:  testcases for the fs error classes functions
@@ -24,3 +25,8 @@ class TestErrorPickling(unittest.TestCase):
         assert_dump_load(UnsupportedError("makepony"))
 
 
+class TestFSError(unittest.TestCase):
+
+    def test_unicode_representation_of_error_with_non_ascii_characters(self):
+        path_error = PathError('/Shïrê/Frødø')
+        _ = unicode(path_error)
\ No newline at end of file