Import order for fiona and rasterio

With the current binary wheels on PyPI, the order that fiona and rasterio are imported into a script/module is important.

Good:

import fiona
import rasterio

Bad:

import rasterio
import fiona

Steps to reproduce

To reproduce the issue (on linux), use a virtual environment to install the current binary wheels from pip:

$ python3 -m venv /tmp/venv
$ . /tmp/venv/bin/activate
(venv) $ pip install fiona rasterio

(installs Fiona-1.8.18-cp36-cp36m-manylinux1_x86_64.whl, rasterio-1.2.1-cp36-cp36m-manylinux1_x86_64.whl, and dependancies)

Importing rasterio before fiona is no good

(venv) $ python -c "import rasterio; import fiona"
ERROR 4: Unable to open EPSG support file gcs.csv.  Try setting the GDAL_DATA environment variable to point to the directory containing EPSG csv files.

The transform module does not work well:

(venv) $ python -c "import rasterio; from fiona.transform import transform; print(transform('EPSG:3857', 'EPSG:4326', [19455906], [-5026598]))"
ERROR 4: Unable to open EPSG support file gcs.csv.  Try setting the GDAL_DATA environment variable to point to the directory containing EPSG csv files.
ERROR 4: Unable to open EPSG support file gcs.csv.  Try setting the GDAL_DATA environment variable to point to the directory containing EPSG csv files.
ERROR 4: Unable to open EPSG support file gcs.csv.  Try setting the GDAL_DATA environment variable to point to the directory containing EPSG csv files.
ERROR 6: No translation for an empty SRS to PROJ.4 format is known.
ERROR 10: Pointer 'hTransform' is NULL in 'OCTTransform'.

([19455906.0], [-5026598.0])

these are the same coordinates as the input, as it’s a failed operation.

Importing fiona before rasterio is OK

(venv) $ python -c "import fiona; import rasterio"

shows no error message, and the transform module works as expected:

(venv) $ python -c "from fiona.transform import transform; import rasterio; print(transform('EPSG:3857', 'EPSG:4326', [19455906], [-5026598]))"
([174.77537726192696], [-41.09658239799418])

these are the expected long, lat coords.

Other discussion

This does not seem to be an issue with packages installed via conda (with conda-forge), testing with rasterio-1.2.1 and fiona-1.8.18. This appears to be an issue while setting GDAL_DATA within the pip package directory. There are some similarities to #673.

[sgillies]

Fixed in 1.8.19.

[jorisvandenbossche]

Also fiona edits the environment variables:

https://github.com/Toblerity/Fiona/blob/885dbd11c5dcb2c61862faefc28bfbbff99954de/fiona/env.py#L590-L601

That could maybe also be changed?