Rasterio and GDAL should not both be imported in the same Python program #359

Describe the bug
It is recommended to avoid importing gdal and rasterio in the same Python program. According to https://rasterio.readthedocs.io/en/latest/topics/switch.html#mutual-incompatibilities:

Rasterio and GDAL’s bindings can contend for global GDAL objects. Unless you have deep knowledge about both packages, choose exactly one of import osgeo.gdal or import rasterio.

GDAL’s bindings (gdal for the rest of this document) and Rasterio are not entirely compatible and should not, without a great deal of care, be imported and used in a single Python program.

To Reproduce
rasterio is imported at the head of gemgis/raster.py (line 25) and gdal is imported in the same file (line 2737).