fix finder.find_module and cm.register_cmap

nansat/nansat.py

@@ -1601,7 +1601,7 @@ def _import_mappers(log_level=None):
             logger.debug('Loading mapper %s' % name)
             # Only mappers containing 'mapper' in the module name should be returned
             if not 'mapper' in name: continue
-            loader = finder.find_module(name)
+            loader = finder.find_spec(name).loader
             # try to import mapper module
             module = loader.load_module(name)
             # add the imported mapper to nansat_mappers

nansat/utils.py

@@ -124,12 +124,6 @@ def register_colormaps():
         }
     }
 
-    if MATPLOTLIB_IS_INSTALLED:
-        for name, colormap in colormaps.items():
-            if name not in matplotlib.colormaps:
-                cm.register_cmap(cmap=LinearSegmentedColormap(name, colormap, 256))
-
-
 def initial_bearing(lon1, lat1, lon2, lat2):
         """Initial bearing when traversing from point1 (lon1, lat1)
         to point2 (lon2, lat2)