undefined property bad error

[scottdraves]

in groovy if i try to get the value of an undefined value on the beakerx object i get a bad error. to reproduce, create a new groovy notebook and evaluate:

beakerx.nothing

and get this error:

java.lang.RuntimeException: com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'undefined': was expecting ('true', 'false' or 'null')
 at [Source: undefined; line: 1, column: 19]
	at com.twosigma.beakerx.DefaultBeakerXJsonSerializer.fromJson(DefaultBeakerXJsonSerializer.java:59)

instead it should work like python does, which gives this error:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-1-af370edb827d> in <module>()
      1 from beakerx import beakerx
----> 2 beakerx.nothing

~/src/beakerx/beakerx/beakerx/runtime.py in __getattr__(self, name)
    582 
    583     def __getattr__(self, name):
--> 584         return self.get(name)
    585 
    586     def __contains__(self, name):

~/src/beakerx/beakerx/beakerx/runtime.py in get(self, var)
    451         result = autotranslation_get(var)
    452         if result == 'undefined':
--> 453             raise NameError('name \'' + var + '\' is not defined in notebook namespace')
    454         return transformBack(json.loads(result))
    455 

NameError: name 'nothing' is not defined in notebook namespace

also, change the python error. we don't call it the notebook namespace anymore.
just say "name 'nothing' is not defined on the beakerx object"