`get_projection_info()` returns null epsg with rasterio 1.4.2

[remicres]

Hi,

I just have submitted an issue on rasterio.
It looks like get_projection_info() returns a None epsg code, since it uses is_epsg_code crom rasterio's CRS class which seems to be faulty to me. to_epsg() returns the correct code though.

[vincentsarago]

I've excluded rasterio 1.4.2 version for now

#63