If the NIX_PATH shadows internal files, this will often break things,
hence we forbid it.
Fixes#998
Change-Id: I70e5d389532ada1c9f910c60281abe565e3ce6bb
While the err file should always be empty, we prefer not have (easily
avoidable) warnings in the log, in order for actual warnings to be
spotted more easily.
Additionally this way no additional changes are required in case they
make use of some depreacted features in the future.
Change-Id: Ie078e2a851b2035d839f6b95d4188e475eb96b2d