* Test for upcoming GDAL feature (from 3.3) allowing existing overviews to
not be exposed
- see https://github.com/OSGeo/gdal/pull/3181
- see https://rasterio.groups.io/g/main/message/649
The test:
- requires gdal 3.3
- tests whether a dataset can be opened with OVERVIEW_LEVEL=-1
- ensures that opening a dataset with OVERVIEW_LEVEL=-1 ignores the file
overview
- ensures that a decimated read on a dataset opened with
OVERVIEW_LEVEL=1 does not read the file overview
* Make test for ignoring overviews when performing decimated read more
simple and robust
The Resampling.average enum value had a comma after it, which caused
that particular enum to map to a tuple instead of a string. This broke
the use of the average kernel when making overviews.