cannot reload sumocfg if SUMO_HOME is not set

[behrisch]

complains about invalid document structure

[namdre]

is this a regression?

[behrisch]

Yes, it has been introduced when we restrained schema checking to local files by default in #11054

[namdre]

Why does the initial load work but not the reload?

[behrisch]

It seems there is something broken in the validation initialization. The first pass does not do any validation (but only in the case without SUMO_HOME)

[namdre]

I would say this is a feature. Much better to load without validation then to not load at all. Giving a warning of validation not possible, please set SUMO_HOME is enough in my view. (And the same for reload).

[behrisch]

You are right, the broken part is that it does validation in the second pass