ConfigurablesUser problem with Python >= 3.7

some tests fail with

Traceback (most recent call last):
  File ".../Gaudi/GaudiKernel/python/GaudiKernel/Configurable.py", line 1570, in applicableConfUsers
    yield next(c for c in Configurable.allConfigurables.values()
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File ".../Gaudi/GaudiExamples/scripts/Aida2RootEx.py", line 180, in <module>
    gaudi = AppMgr()
  File ".../Gaudi/GaudiPython/python/GaudiPython/Bindings.py", line 937, in __new__
    cls.__init__(newobj, *args, **kwargs)
  File ".../Gaudi/GaudiPython/python/GaudiPython/Bindings.py", line 1002, in __init__
    GaudiKernel.Proxy.Configurable.applyConfigurableUsers()
  File ".../Gaudi/GaudiKernel/python/GaudiKernel/Configurable.py", line 1574, in applyConfigurableUsers
    for c in applicableConfUsers():
RuntimeError: generator raised StopIteration