Replace deprecated dedent function by a similar function.

Fix issue #495

Author: joernu76

lib/mpl_toolkits/basemap/proj.py

@@ -3,7 +3,12 @@
 import numpy as np
 import pyproj
 import math
-from matplotlib.cbook import dedent
+try:
+    from inspect import cleandoc as dedent
+except ImportError:
+    # Deprecated as of version 3.1. Not quite the same
+    # as textwrap.dedent.
+    from matplotlib.cbook import dedent
 
 __version__ = '1.2.2'
 _dg2rad = math.radians(1.)