Fixes to factory to handle ignore_external.

[TeresiaOlsson]

This is to fix issue #292.

I have added so the factory returns None instead of building an object if ignore_external = True and the module isn't found.

I had to also add a fix in the linear magnet module to handle the case when the powerconverter becomes None.

[TeresiaOlsson]

The issue is now that sr.live just isn't created. Feels like it rather should be None. Or what do you think?

[JeanLucPons]

Yes that's normal that sr.live is not created as the module is unknown but you can still use the rest such as sr.design.
This is the expected behavior.

[TeresiaOlsson]

So you want this error if the user does sr.live?

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
Cell In[7], line 1
----> 1 sr.live

File ~/Documents/software/pyAML/pyaml/pyaml/accelerator.py:219, in Accelerator.live(self)
    209 @property
    210 def live(self) -> ControlSystem:
    211     """
    212     Get the live control system.
    213 
   (...)    217         The live control system instance
    218     """
--> 219     return self.__live

AttributeError: 'Accelerator' object has no attribute '_Accelerator__live'

I thought maybe it would be better to return None?

[JeanLucPons]

Yes for me it is fine.

[TeresiaOlsson]

Maybe it is just that:

        __design = None
        __live = None

Should be:

        self.__design = None
        self.__live = None

and the error will be gone.

[TeresiaOlsson]

Yes, that would fix it. Unless there is a reason why those two attributes doesn't have self before?