nbconvert errors for notebook requiring auto translation

When running notebook via jupyter nbconvert --execute, the beakerx extension is not enabled. As a result, I am getting exception:
```
/usr/lib/python3.7/os.py in __getitem__(self, key)
676 except KeyError:
677 # raise KeyError with the original key value
--> 678 raise KeyError(key) from None
679 return self.decodevalue(value)
680

KeyError: 'BEAKERX_AUTOTRANSLATION_PORT'
KeyError: 'BEAKERX_AUTOTRANSLATION_PORT'
```
when executing notebooks which require auto translation (notebooks which mix multiple languages. In my example, it was python mixed with java).

Is there a way to enable beakerx for nbconvert already? or can we add it as a feature?