CLN: Include explicit error when module not known in pickle helper

Author: Sheppard, Kevin

README.md

@@ -1,5 +1,6 @@
 # ng-numpy-randomstate
-[![Build Status](https://travis-ci.org/bashtage/ng-numpy-randomstate.svg?branch=master)](https://travis-ci.org/bashtage/ng-numpy-randomstate)
+[![Build Status](https://travis-ci.org/bashtage/ng-numpy-randomstate.svg?branch=master)](https://travis-ci.org/bashtage/ng-numpy-randomstate) 
+[![Build status](https://ci.appveyor.com/api/projects/status/odc5c4ukhru5xicl/branch/master?svg=true)](https://ci.appveyor.com/project/bashtage/ng-numpy-randomstate/branch/master)
 
 This is a library and generic interface for alternative random generators 
 in Python and Numpy. This modules includes a number of alternative random 

randomstate/prng/__init__.py

@@ -42,5 +42,7 @@ def __generic_ctor(mod_name='mt19937'):
         mod = xorshift128
     elif mod_name == 'xorshift1024':
         mod = xorshift1024
+    else:
+        raise ValueError(str(mod_name) + ' is not a known PRNG module.')
 
     return mod.RandomState(0)