make error classes pickleable, and add appropriate tests

fs/errors.py

@@ -37,12 +37,15 @@ class FSError(Exception):
     def __unicode__(self):
         return unicode(str(self))
 
+    def __getstate__(self):
+       return self.__dict__.copy()
+
 
 class PathError(FSError):
     """Exception for errors to do with a path string."""
     default_message = "Path is invalid: %(path)s"
 
-    def __init__(self,path,**kwds):
+    def __init__(self,path="",**kwds):
         self.path = path
         super(PathError,self).__init__(**kwds)
  
@@ -51,7 +54,7 @@ class OperationFailedError(FSError):
     """Base exception class for errors associated with a specific operation."""
     default_message = "Unable to %(opname)s: unspecified error [%(errno)s - %(details)s]"
 
-    def __init__(self,opname,path=None,**kwds):
+    def __init__(self,opname="",path=None,**kwds):
         self.opname = opname
         self.path = path
         self.errno = getattr(kwds.get("details",None),"errno",None)
@@ -82,7 +85,7 @@ class ResourceError(FSError):
     """Base exception class for error associated with a specific resource."""
     default_message = "Unspecified resource error: %(path)s"
 
-    def __init__(self,path,**kwds):
+    def __init__(self,path="",**kwds):
         self.path = path
         self.opname = kwds.pop("opname",None)
         super(ResourceError,self).__init__(**kwds)

fs/tests/test_errors.py

+"""
+
+  fs.tests.test_errors:  testcases for the fs error classes functions
+
+"""
+
+
+import unittest
+import fs.tests
+from fs.errors import *
+import pickle
+
+from fs.path import *
+
+class TestErrorPickling(unittest.TestCase):
+
+    def test_pickling(self):
+        def assert_dump_load(e):
+            e2 = pickle.loads(pickle.dumps(e))
+            self.assertEqual(e.__dict__,e2.__dict__)
+        assert_dump_load(FSError())
+        assert_dump_load(PathError("/some/path"))
+        assert_dump_load(ResourceNotFoundError("/some/other/path"))
+        assert_dump_load(UnsupportedError("makepony"))
+
+