use local file if ellips server returns a HTTPError

[OnnoEbbens]

Added a geojson with the ahn tiles and a function _get_tiles_from_file to prevent HTTPErrors when retrieving the tiles from the ellips server.

I considered removing the _get_tiles_ellipsis function and always use the geojson but then updates and changes to this file will go unnoticed, that's why I left the original function and added a try/except.

[bdestombe]

Added a geojson with the ahn tiles and a function _get_tiles_from_file to prevent HTTPErrors when retrieving the tiles from the ellips server.

I considered removing the _get_tiles_ellipsis function and always use the geojson but then updates and changes to this file will go unnoticed, that's why I left the original function and added a try/except.

What about adding a test that checks whether the local geojson is the same as the one served from the ellips server?

[rubencalje]

Ah, I merged this PR, but I may have been a bit too quick, sorry.

The columns in EllipsisDrive_index_fancy.geojson are different from the columns you normally retrieve using _get_tiles_ellipsis: for example "AHN3 maaiveldmodel (DTM) ½m" instead of "AHN3_05M_M".

I will add a fix and implement the suggestion by @bdestombe.

[rubencalje]

Ah, I merged this PR, but I may have been a bit too quick, sorry.

The columns in EllipsisDrive_index_fancy.geojson are different from the columns you normally retrieve using _get_tiles_ellipsis: for example "AHN3 maaiveldmodel (DTM) ½m" instead of "AHN3_05M_M".

I will add a fix and implement the suggestion by @bdestombe.

I fixed the AHN in PR #383. By default, we now use the geojson-file for the metadata of the tiles, and I added a test that checks if the geojson-file is upto-date.