Fix a namespace warning when importing gdal directly [rebase on PyWPS 4.4]

[Zeitsperre]

Overview

This is a very small fix needed to squelch a warning that shows up with GDAL:

../../miniconda3/envs/raven-dev/lib/python3.8/site-packages/osgeo/gdal.py:106
  /home/tjs/miniconda3/envs/raven-dev/lib/python3.8/site-packages/osgeo/gdal.py:106: DeprecationWarning: gdal.py was placed in a namespace, it is now available as osgeo.gdal
    warn('%s.py was placed in a namespace, it is now available as osgeo.%s' % (module,module),

Related Issue / Discussion

Additional Information

Contribution Agreement

(as per https://github.com/geopython/pywps/blob/master/CONTRIBUTING.rst#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to PyWPS. I confirm that my contributions to PyWPS will be compatible with the PyWPS license guidelines at the time of contribution.
• I have already previously agreed to the PyWPS Contributions and Licensing Guidelines

[coveralls]

Coverage remained the same at 0.0% when pulling 7307e70 on pywps-4.4-fix-gdal-warning into d593f4a on pywps-4.4.