Fix for issue #89(Improve savestate error handling)

command_callbacks.py

@@ -1754,6 +1754,12 @@ def savestate_filename(input_dict, environment_dict):
                            environment_dict['cmdargs'], environment_dict['defaulttarget'], 
                            environment_dict['defaultkeyname'], environment_dict['autosave'], 
                            environment_dict['currentkeyname'])
+  except TypeError:
+    raise seash_exceptions.UserError("Please load at least a pubkey, and work as that identity.")
+
+  except UnboundLocalError:
+    raise seash_exceptions.UserError("Don't use savestate to a write-protected file.")
+
   except Exception, error:
     raise seash_exceptions.UserError("Error saving state: '" + str(error) + "'.")
 

tests/ut_seash_savestate_nicermessage.py

@@ -0,0 +1,38 @@
+"""
+This unit test is to test error messages at these situations. One is using 
+savestate before having loaded at least a pubkey, and work as that identity.
+Another is using savestate to a write-protected file.   
+"""
+
+import seash
+import sys
+import os
+import seash_exceptions
+
+#pragma out Please load at least a pubkey, and work as that identity.
+#pragma out Don't use savestate to a write-protected file.
+
+open('write_protected_file', 'w+').close()
+os.system('chmod a-w write_protected_file')
+
+command_list = [ 
+  'savestate NO_KEYS_LOADED',
+]
+
+try:
+  seash.command_loop(command_list)
+except seash_exceptions.UserError, e:
+  print str(e)
+
+command_list = [
+  'loadkeys guest0', 
+  'as guest0', 
+  'savestate write_protected_file',
+]
+
+try:
+  seash.command_loop(command_list)
+except seash_exceptions.UserError, e:
+  print str(e)
+
+os.remove('write_protected_file')