BIND 10 #294: friendlier error for incompatible/old configuration database

[BIND 10 Development]

#294: friendlier error for incompatible/old configuration database
----------------------------+-----------------------------------------------
  Reporter:  jreed          |            Owner:  jelte
      Type:  defect         |           Status:  new  
  Priority:  major          |        Milestone:       
 Component:  configuration  |         Keywords:       
 Sensitive:  0              |   Estimatedhours:  0    
     Hours:  .25            |         Billable:  1    
Totalhours:  0              |         Internal:  0    
----------------------------+-----------------------------------------------
 {{{
 [bind10] Starting b10-cfgmgr
 [bind10] Started b10-cfgmgr (PID 5520)
 Traceback (most recent call last):
   File "/home/reed/opt/bind10/lib/python3.1/site-
 packages/isc/config/cfgmgr.py", line 70, in read_from_file
     file_config = json.loads(file.read())
   File "/usr/pkg/lib/python3.1/json/__init__.py", line 291, in loads
     return _default_decoder.decode(s)
   File "/usr/pkg/lib/python3.1/json/decoder.py", line 325, in decode
     obj, end = self.raw_decode(s, idx=_w(s, 0).end())
   File "/usr/pkg/lib/python3.1/json/decoder.py", line 341, in raw_decode
     obj, end = self.scan_once(s, idx)
 ValueError: Expecting property name: line 1 column 1 (char 1)

 During handling of the above exception, another exception occurred:

 Traceback (most recent call last):
   File "/home/reed/opt/bind10/libexec/bind10-devel/b10-cfgmgr", line 61,
 in <module>
     main()
   File "/home/reed/opt/bind10/libexec/bind10-devel/b10-cfgmgr", line 49,
 in main
     cm.read_config()
   File "/home/reed/opt/bind10/lib/python3.1/site-
 packages/isc/config/cfgmgr.py", line 210, in read_config
     self.config = ConfigManagerData.read_from_file(self.data_path)
   File "/home/reed/opt/bind10/lib/python3.1/site-
 packages/isc/config/cfgmgr.py", line 81, in read_from_file
     raise ConfigManagerDataReadError("Config file unreadable")
 isc.config.cfgmgr.ConfigManagerDataReadError: Config file unreadable
 }}}

 Have a nice error message instead of this trace. Like if fails on input of
 old db, then that could say "out of date or corrupt".

 I understand that documentation may be used to help teach how to update
 and this is a development release so no tool is needed for upgrade.

 Also bump the version number (even though that would not have helped this
 time).

-- 
Ticket URL: <https://bind10.isc.org/ticket/294>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development