bump minimum python versions

[jhamman]

No description provided.

[scottyhq]

docs failing b/c AWS Landsat public dataset no longer exists

https://github.com/intake/intake-stac/blob/main/docs/source/tutorial.rst#loading-a-catalog ->

https://raw.githubusercontent.com/sat-utils/sat-stac/master/test/catalog ->

https://landsat-pds.s3.amazonaws.com/c1/L8/107/018/LC08_L1TP_107018_20181001_20181001_01_RT/LC08_L1TP_107018_20181001_20181001_01_RT_B1.TIF

[scottyhq]

test_drivers_include_all_pystac_media_types test failing with upstream environment:

AssertionError: assert <MediaType.PDF: 'application/pdf'> in {'application/geo+json': 'geopandas', 'application/geopackage+sqlite3': 'geopandas', 'application/json': 'textfiles', 'application/netcdf': 'netcdf', ...}

So pystac has added the application/pdf media type, which looks like is used for things like product documentation links: https://github.com/stac-utils/pystac/blob/a8f50cba92e27c9e1630bb8332523e9d06ee9cc4/tests/data-files/examples/1.0.0-beta.2/extensions/sar/examples/envisat.json#L80-L82

    "links": [
        {
            "rel": "about",
            "href": "https://earth.esa.int/pub/ESA_DOC/ENVISAT/ASAR/asar.ProductHandbook.2_2.pdf",
            "title": "ASAR Product Handbook",
            "type": "application/pdf"
        },

I'm just going to add a special case to that test...

[scottyhq]

@jhamman - gave the CI a much needed update, and I think we're good to go now if you want to merge this, add to the changelog, and release 0.4.