qualify Core module

[t-bltg]

ERROR: LoadError: InitError: Python: Julia: UndefVarError: `Core` not defined in `PythonCall.Compat`
Hint: It looks like two or more modules export different bindings with this name, resulting in ambiguity. Try explicitly importing it from a particular module, or qualifying the name with the module it should come from.
Hint: a global variable of this name also exists in Core.
Stacktrace:
  [1] (::PythonCall.Compat.var"#1#2")()
    @ PythonCall.Compat [...]/.julia/packages/PythonCall/mkWc2/src/Compat/gui.jl:162

Qualify explicitly the Core module to avoid LoadError.

[cjdoris]

Thanks but it's already fixed in #683