Tk error when starting widget in a headless environment

[jonashaase]

Hi

Starting the widget inside a notebook running inside a headless docker container currently yields an error.
I see the initialisation has changes recently regarding how Tk is used.
Is there a way the environment has to be set up in the container so this works again?
Or could this perhaps again be made agnostic towards whether or not a display exists?

cheers
Jonas

TclErrorTraceback (most recent call last)
<ipython-input-1-0616404e5e7e> in <module>
      1 from pyesasky import ESASkyWidget
----> 2 esasky = ESASkyWidget()
      3 esasky

~/miniconda3/lib/python3.8/site-packages/pyesasky/pyesasky.py in __init__(self, lang)
     47     def __init__(self, lang = 'en'):
     48         super().__init__()
---> 49         tk = Tk()
     50         tk.withdraw()
     51         tk.call('wm', 'attributes', '.', '-topmost', True)

~/miniconda3/lib/python3.8/tkinter/__init__.py in __init__(self, screenName, baseName, className, useTk, sync, use)
   2268                 baseName = baseName + ext
   2269         interactive = 0
-> 2270         self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
   2271         if useTk:
   2272             self._loadtk()

TclError: no display name and no $DISPLAY environment variable