Handle owslib across python versions

Author: amercader

requirements.txt

@@ -4,9 +4,12 @@ argparse
 pyparsing>=2.1.10
 requests>=1.1.0
 cython==0.29.36; python_version < '3.9'
+
 pyproj==2.6.1; python_version < '3.9'
 pyproj==3.6.1; python_version >= '3.9'
 
+OWSLib==0.31.0; python_version < '3.9'
+OWSLib==0.32.0; python_version >= '3.9'
+
 Shapely==2.0.6
-OWSLib==0.32.0
 geojson==3.1.0