Trying to avoid formula:firewall error using python script

Hi Guys,

i have the code like here:

= fnGetPath("BUNDLES_PATH_TEST")

- this is my function with argument refrencing to windows environment.

Function is:

let
    GetPath = (envVariable as text) =>
    let
        Source = Python.Execute("
import os
import pandas as pd

env_value = os.getenv(envVariable)

data = [[env_value]]
df = pd.DataFrame(data, columns=['Path'])
"),
        df1 = Source{[Name="df"]}[Value],
        Path = df1{0}[Path]
    in
        Path
in
    GetPath

without function is working. 
But I am getting formula:firewall issue. 

So i need to have a function but seems that power query is not consuming my passed argument as text...

Please help,
Jacek