* Raise WarpOperationError (new) if ChunkAndWarpMulti/Image fail
We've been hiding these errors and allowing chunks of a warp
operation to pass with no data copied to the output.
Note that the error message isn't very detailed. In a lot of
cases it's a generic "TIFF read block error" and doesn't surface
root causes like server errors.
* Temporarily home in on one test
* Make 503 more predictable
The exact request range varies a little bit with GDAL version
* Skip test on pythons < 3.7
